Southwest Airlines (LUV) 10-K 8 Feb 21 2020 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 04, 2021	Jun. 30, 2020
Entity Incorporation, State or Country Code	TX
Entity Tax Identification Number	74-1563240
Document Transition Report	false
Document Annual Report	true
Entity Address, Address Line One	P.O. Box 36611
Entity Address, City or Town	Dallas,
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75235-1611
City Area Code	214
ICFR Auditor Attestation Flag	true
Local Phone Number	792-4000
Title of 12(g) Security	None
Entity Registrant Name	SOUTHWEST AIRLINES CO.
Entity Central Index Key	0000092380
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2020
Entity File Number	1-7259
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		590,677,474
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Public Float			$ 20,094,518,012
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
NEW YORK STOCK EXCHANGE, INC. [Member]
Title of 12(b) Security	Common Stock ($1.00 par value)
Trading Symbol	LUV
Security Exchange Name	NYSE

Consolidated Balance Sheet

Consolidated Balance Sheet - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 11,063	$ 2,548
Short-term investments	2,271	1,524
Accounts and other receivables	1,130	1,086
Inventories of parts and supplies, at cost	414	529
Prepaid expenses and other current assets	295	287
Total current assets	15,173	5,974
Property and equipment, at cost:
Flight equipment	20,877	21,629
Ground property and equipment	6,083	5,672
Deposits on flight equipment purchase contracts	305	248
Assets constructed for others	309	164
Property and equipment, at cost	27,574	27,713
Less allowance for depreciation and amortization	11,743	10,688
Property and equipment, net	15,831	17,025
Goodwill	970	970
Operating lease right-of-use assets	1,892	1,349
Total assets	34,588	25,895
Current liabilities:
Accounts payable	931	1,574
Accrued liabilities	2,259	1,749
Current operating lease liabilities	306	353
Air traffic liability	3,790	4,457
Current maturities of long-term debt	220	819
Total current liabilities	7,506	8,952
Long-term debt less current maturities	10,111	1,846
Air traffic liability - noncurrent	3,343	1,053
Deferred income taxes	1,634	2,364
Construction obligation	309	164
Noncurrent operating lease liabilities	1,562	978
Other noncurrent liabilities	1,247	706
Stockholders' equity:
Common stock, $1.00 par value: 2,000,000,000 shares authorized; 888,111,634 and 807,611,634 shares issued in 2020 and 2019 respectively	888	808
Capital in excess of par value	4,191	1,581
Retained earnings	14,777	17,945
Accumulated other comprehensive income (loss)	(105)	(61)
Treasury stock, at cost: 297,637,297 and 288,547,318 shares in 2020 and 2019 respectively	(10,875)	(10,441)
Total stockholders' equity	8,876	9,832
Total liabilities and stockholders' equity	$ 34,588	$ 25,895
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	2,000,000,000	2,000,000,000
Common stock, shares issued (in shares)	888,111,634	807,611,634
Treasury stock, at cost: shares (in shares)	297,637,297	288,547,318

Consolidated Statement of Incom

Consolidated Statement of Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
OPERATING REVENUES:
Operating Revenue	$ 9,048	$ 22,428	$ 21,965
OPERATING EXPENSES, NET:
Salaries, wages, and benefits	6,811	8,293	7,649
Payroll support and voluntary Employee programs, net	(967)	0	0
Fuel and oil	1,849	4,347	4,616
Maintenance materials and repairs	750	1,223	1,107
Landing fees and airport rentals	1,240	1,363	1,334
Depreciation and amortization	1,255	1,219	1,201
Other operating expenses	1,926	3,026	2,852
Total operating expenses, net	12,864	19,471	18,759
OPERATING INCOME (LOSS)	(3,816)	2,957	3,206
OTHER EXPENSES (INCOME):
Interest expense	349	118	131
Capitalized interest	(35)	(36)	(38)
Interest income	(32)	(90)	(69)
Other (gains) losses, net	(158)	(8)	(18)
Total other expenses (income)	440	0	42
INCOME (LOSS) BEFORE INCOME TAXES	(4,256)	2,957	3,164
PROVISION (BENEFIT) FOR INCOME TAXES	(1,182)	657	699
NET INCOME (LOSS)	$ (3,074)	$ 2,300	$ 2,465
NET INCOME (LOSS) PER SHARE, BASIC	$ (5.44)	$ 4.28	$ 4.30
NET INCOME (LOSS) PER SHARE, DILUTED	$ (5.44)	$ 4.27	$ 4.29
Passenger
OPERATING REVENUES:
Operating Revenue	$ 7,665	$ 20,776	$ 20,455
Freight
OPERATING REVENUES:
Operating Revenue	161	172	175
Other
OPERATING REVENUES:
Operating Revenue	$ 1,222	$ 1,480	$ 1,335

Consolidated Statement of Compr

Consolidated Statement of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net income (loss)	$ (3,074)	$ 2,300	$ 2,465
Unrealized gain (loss) on defined benefit plan items, net of deferred taxes of ($15), ($9), and $15	(48)	(29)	52
Other, net of deferred taxes of $7, $8, and ($2)	25	26	(6)
OTHER COMPREHENSIVE INCOME (LOSS)	(44)	(81)	26
COMPREHENSIVE INCOME (LOSS)	(3,118)	2,219	2,491
Operating Revenue	9,048	22,428	21,965
Supplemental Income Statement Elements [Abstract]
Deferred taxes on postretirement	(15)	(9)	15
Deferred taxes on unrealized gain (loss), other, tax effect	7	8	(2)
Passenger
Operating Revenue	7,665	20,776	20,455
Freight
Operating Revenue	161	172	175
Other
Operating Revenue	1,222	1,480	1,335
Fuel derivatives
Unrealized gain (loss) on derivatives, net of tax	4	(53)	(26)
Supplemental Income Statement Elements [Abstract]
Deferred taxes on unrealized gain (loss) on derivatives, tax effect	2	(16)	(7)
Interest rate derivatives
Unrealized gain (loss) on derivatives, net of tax	(25)	(25)	6
Supplemental Income Statement Elements [Abstract]
Deferred taxes on unrealized gain (loss) on derivatives, tax effect	$ (8)	$ (8)	$ 1

Consolidated Statement of Stock

Consolidated Statement of Stockholder's Equity - USD ($) $ in Millions	Total	Common Stock	Capital in excess of par value	Retained earnings	Accumulated other comprehensive income (loss)	Treasury stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of new accounting standards	$ 0	$ 0	$ 0	$ 18	$ (18)	$ 0
Balance at beginning of period at Dec. 31, 2017	9,641	808	1,451	13,832	12	(6,462)
Balance at beginning of period (ASU 2017-12) at Dec. 31, 2017	9,641	808	1,451	13,850	(6)	(6,462)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of common stock	(2,000)	0	0	0	0	(2,000)
Issuance of common and treasury stock pursuant to Employee stock plans	23	0	13	0	0	10
Share-based compensation	46	0	46	0	0	0
Cash dividends	$ (348)	0	0	(348)	0	0
Cash dividends, per share (in dollars per share)	$ 0.605
Comprehensive income (loss)	$ 2,491	0	0	2,465	26	0
Balance at end of period at Dec. 31, 2018	9,853	808	1,510	15,967	20	(8,452)
Balance at end of period (ASU 2016-02) at Dec. 31, 2018	9,908	808	1,510	16,022	20	(8,452)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of new accounting standards	55	0	0	55	0	0
Repurchase of common stock	(2,000)	0	0	0	0	(2,000)
Issuance of common and treasury stock pursuant to Employee stock plans	27	0	16	0	0	11
Share-based compensation	55	0	55	0	0	0
Cash dividends	$ (377)	0	0	(377)	0	0
Cash dividends, per share (in dollars per share)	$ 0.700
Comprehensive income (loss)	$ 2,219	0	0	2,300	(81)	0
Balance at end of period at Dec. 31, 2019	9,832	808	1,581	17,945	(61)	(10,441)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of common stock	(451)	0	0	0	0	(451)
Issuance of common stock, net of issuance costs	2,224	80	2,144	0	0	0
Issuance of common and treasury stock pursuant to Employee stock plans	34	0	17	0	0	17
Share-based compensation	17	0	17	0	0	0
Cash dividends	$ (94)	0	0	(94)	0	0
Cash dividends, per share (in dollars per share)	$ 0.180
Stock warrants	$ 40	0	40	0	0	0
Equity feature of convertible notes, net of issuance costs	392	0	392	0	0	0
Comprehensive income (loss)	(3,118)	0	0	(3,074)	(44)	0
Balance at end of period at Dec. 31, 2020	$ 8,876	$ 888	$ 4,191	$ 14,777	$ (105)	$ (10,875)

Consolidated Statement of Cash

Consolidated Statement of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ (3,074)	$ 2,300	$ 2,465
Adjustments to reconcile net income (loss) to cash provided by (used in) operating activities:
Depreciation and amortization	1,255	1,219	1,201
Loss on asset impairment	32	0	0
Unrealized/realized (gain) loss on fuel derivative instruments	15	0	(14)
Deferred income taxes	(716)	(55)	301
Gain on sale-leaseback transactions	(222)	0	0
Changes in certain assets and liabilities:
Accounts and other receivables	(294)	(94)	117
Other assets	415	239	(227)
Accounts payable and accrued liabilities	231	298	545
Air traffic liability	1,623	440	506
Other liabilities	(306)	(277)	0
Cash collateral received from (provided to) derivative counterparties	9	25	(15)
Other, net	(95)	(108)	14
Net cash provided by (used in) operating activities	(1,127)	3,987	4,893
Net Cash Provided by (Used in) Investing Activities [Abstract]
Capital expenditures	(515)	(1,027)	(1,922)
Supplier Proceeds	428	400	0
Proceeds from sale-leaseback transactions	815	0	0
Assets constructed for others	0	0	(54)
Purchases of short-term investments	(5,080)	(2,122)	(2,409)
Proceeds from sale of short-term and other investments	4,336	2,446	2,342
Other, net	0	0	5
Net cash used in investing activities	(16)	(303)	(2,038)
Net cash provided by (used in) financing activities
Issuance of common stock	2,294	0	0
Proceeds from issuance of long-term debt	5,622	0	0
Proceeds from term loan credit facility	3,683	0	0
Proceeds from revolving credit facility	1,000	0	0
Proceeds from convertible notes	2,300	0	0
Proceeds from Payroll support program loans and warrants	1,016	0	0
Proceeds from Employee stock plans	48	40	35
Repurchase of common stock	(451)	(2,000)	(2,000)
Reimbursement for assets constructed for others	0	0	170
Payments of long-term debt and finance lease obligations	(839)	(615)	(342)
Payments of cash dividends	(188)	(372)	(332)
Payments of terminated interest rate derivative instruments	(59)	0	0
Repayment of construction obligation	0	0	(30)
Capitalized financing items	(134)	0	0
Other, net	49	(43)	3
Net cash provided by (used in) financing activities	9,658	(2,990)	(2,496)
NET CHANGE IN CASH AND CASH EQUIVALENTS	8,515	694	359
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	2,548	1,854	1,495
CASH AND CASH EQUIVALENTS AT END OF PERIOD	11,063	2,548	1,854
CASH PAYMENTS FOR:
Interest, net of amount capitalized	212	88	107
Income taxes	19	779	327
SUPPLEMENTAL DISCLOSURE OF NONCASH TRANSACTIONS:
Assets constructed for others	145	65	171
Supplier receivables	0	428	0
Revolving Credit Facility
Net cash provided by (used in) financing activities
Payments of revolving credit facility	(1,000)	0	0
364-Day Term Loan Credit Facility
Net cash provided by (used in) financing activities
Payments of term loan credit facility	$ (3,683)	$ 0	$ 0

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation Southwest Airlines Co. (the "Company") operates Southwest Airlines, a major domestic airline. The Consolidated Financial Statements include the accounts of the Company and its wholly owned subsidiaries, which include AirTran Holdings, LLC, the successor to AirTran Holdings, Inc. ("AirTran Holdings"), the former parent company of AirTran Airways, Inc., and Triple Crown Assurance Co., an insurance captive. The accompanying Consolidated Financial Statements include the results of operations and cash flows for all periods presented and all significant inter-entity balances and transactions have been eliminated. The preparation of financial statements in conformity with generally accepted accounting principles in the United States ("GAAP") requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from these estimates. Effective as of January 1, 2019, the Company adopted Accounting Standards Update ("ASU") No. 2016-02, Leases, codified in Accounting Standards Codification ("ASC") 842 (the "New Lease Standard"). All amounts and disclosures set forth in this Form 10-K, reflect the adoption of this ASU, while all periods prior to 2019 remain in accordance with prior accounting requirements. See Note 3 for further information. Cash and Cash Equivalents Cash in excess of that necessary for operating requirements is invested in short-term, highly liquid, income-producing investments. Investments with original maturities of three months or less when purchased are classified as cash and cash equivalents, which primarily consist of certificates of deposit, money market funds, and investment grade commercial paper issued by major corporations and financial institutions. Cash and cash equivalents are stated at cost, which approximates fair value. As of December 31, 2020 and 2019, $34 million and $25 million, respectively, in cash collateral deposits were held by the Company from its fuel hedge counterparties, and no cash collateral deposits were held by or provided by the Company to its interest rate hedge counterparties for both periods. Cash collateral amounts provided or held associated with fuel and interest rate derivative instruments are not restricted in any way and earn interest income at an agreed upon rate that approximates the rates earned on short-term securities issued by the U.S. Government. Depending on the fair value of the Company’s fuel and interest rate derivative instruments, the amounts of collateral deposits held or provided at any point in time can fluctuate significantly. See Note 11 for further information on these collateral deposits and fuel derivative instruments. Short-term and Noncurrent Investments Short-term investments consist of investments with original maturities of greater than three months but less than twelve months when purchased. These are primarily short-term securities issued by the U.S. Government and certificates of deposit issued by domestic banks. All of these investments are classified as available-for-sale securities and are stated at fair value, which approximates cost. For all short-term investments, at each reset period or upon reinvestment, the Company accounts for the transaction as Proceeds from sales of short-term investments for the security relinquished, and Purchases of short-investments for the security purchased, in the accompanying Consolidated Statement of Cash Flows. Unrealized gains and losses, net of tax, if any, are recognized in Accumulated other comprehensive income (loss) ("AOCI") in the accompanying Consolidated Balance Sheet. Realized net gains and losses on specific investments, if any, are reflected in Interest income in the accompanying Consolidated Statement of Income (Loss). Both unrealized and realized gains and/or losses associated with investments were immaterial for all years presented. Noncurrent investments consist of investments with maturities of greater than twelve months. Noncurrent investments are included as a component of Other assets in the Consolidated Balance Sheet. Accounts and Other Receivables Accounts and other receivables are initially recorded at cost and are evaluated for collectability in every period. They primarily consist of the amounts due from the Company's business partners and other suppliers, amounts due from business partners in the Company’s loyalty program, and tax receivables from overpayment or net operating losses that are allowed to be carried back to prior periods to claim refunds against prior taxes paid. See Note 16 for further information. The allowance for doubtful accounts was immaterial at December 31, 2020 and 2019. In addition, the provision for doubtful accounts and write-offs for 2020, 2019, and 2018 were each immaterial. Inventories Inventories primarily consist of aircraft fuel, flight equipment expendable parts, materials, and supplies. All of these items are carried at average cost, less an allowance for obsolescence. These items are generally charged to expense when issued for use. The reserve for obsolescence was immaterial at December 31, 2020, and 2019. In addition, the Company’s provision for obsolescence and write-offs for 2020, 2019, and 2018 were each immaterial. Property and Equipment Property and equipment is stated at cost. Capital expenditures include payments made for aircraft, other flight equipment, purchase deposits related to future aircraft deliveries, airport and other facility construction projects, and ground and other property and equipment. Depreciation is provided by the straight-line method to estimated residual values over periods of approximately 25 years for flight equipment, and 5 to 30 years for ground property and equipment. Residual values estimated for aircraft are approximately 15 percent, and generally range from 0 to 10 percent for ground property and equipment. Assets constructed for others consists of airport improvement projects in which the Company is considered to have control of the asset during the construction period. Once construction is effectively completed, the sale-leaseback model would apply when control passes from the lessee to the lessor. See Note 5 for further information. The Company evaluates its long-lived assets used in operations for impairment when events and circumstances indicate that the undiscounted cash flows to be generated by that asset are less than the carrying amounts of the asset and may not be recoverable. Factors that would indicate potential impairment include, but are not limited to, significant decreases in the market value of the long-lived asset(s), a significant change in the long-lived asset’s physical condition, and operating or cash flow losses associated with the use of the long-lived asset. If an asset is deemed to be impaired, an impairment loss is recorded for the excess of the asset book value in relation to its estimated fair value. As a result of the events and impacts surrounding the COVID-19 pandemic, including the Company's net loss incurred during the year ended December 31, 2020, and the significant number of aircraft that have been placed in storage, the Company assessed whether any impairment of its amortizable assets existed. No aircraft impairment charges were deemed necessary for the majority of 2020. For the purpose of impairment assessment, the Company evaluates its all Boeing fleet as one asset group. However, during fourth quarter 2020, the Company made the decision to permanently ground, and accelerate the retirement of, 20 of its 737-700 aircraft as of December 31, 2020. This action resulted in the Company recording $32 million in impairment charges associated with these 20 aircraft. Leases The Company determines if an arrangement is a lease at inception. Operating leases are included in Operating lease right-of-use assets, Current operating lease liabilities, and Noncurrent operating lease liabilities in the Consolidated Balance Sheet. Finance leases are included in Property and equipment, Current maturities of long-term debt, and Long-term debt less current maturities in the Consolidated Balance Sheet. Right-of-use assets represent the Company's right to use an underlying asset for the lease term, and lease liabilities represent the Company's obligation to make lease payments arising from the lease. The lease liability is measured as the present value of the unpaid lease payments, and the right-of-use asset value is derived from the calculation of the lease liability. Lease payments include fixed and in-substance fixed payments, variable payments based on an index or rate, reasonably certain purchase options, termination penalties, fees paid by the lessee to the owners of a special-purpose entity for restructuring the transaction, and probable amounts the lessee will owe under a residual value guarantee. Lease payments do not include (i) variable lease payments other than those that depend on an index or rate, (ii) any guarantee by the lessee of the lessor’s debt, or (iii) any amount allocated to non-lease components, if such election is made upon adoption, per the provisions of the New Lease Standard. The Company uses its estimated incremental borrowing rate, which is derived from information available at the lease commencement date, in determining the present value of lease payments, since the Company does not know the actual implicit rates in its leases. The Company gives consideration to its recent debt issuances as well as publicly available data for instruments with similar characteristics when calculating its incremental borrowing rate. Lease expense for operating lease payments is recognized on a straight-line basis over the lease term. The Company combines lease and nonlease components for all asset groups. The Company's lease term includes any option to extend the lease when it is reasonably certain to be exercised based on considering all relevant economic factors. Aircraft and Engine Maintenance The cost of scheduled inspections and repairs and routine maintenance costs for all aircraft and engines are charged to Maintenance materials and repairs expense within the accompanying Consolidated Statement of Income (Loss) as incurred. The Company has maintenance agreements related to certain of its aircraft engines with external service providers, including agreements that effectively transfer the risk of performance of such work to the service provider. Under the agreements where the risk of performance is deemed transferred to the counterparty, the appropriate expense is recorded commensurate with the period in which the corresponding level of service is provided. Generally, expense is recorded on a straight-line basis over the term of the agreement based on the Company's best estimate of expected future aircraft utilization. For its engine maintenance contracts that do not transfer risk to the service provider, the Company records expense on a time and materials basis when an engine repair event takes place. Modifications that significantly enhance the operating performance or extend the useful lives of aircraft or engines are capitalized and amortized over the remaining life of the asset. Goodwill and Intangible Assets The Company applies a fair value based impairment test to the carrying value of goodwill and indefinite-lived intangible assets annually on October 1st, or more frequently if certain events or circumstances indicate that an impairment loss may have been incurred. The Company assesses the value of goodwill and indefinite-lived intangible assets under either a qualitative or quantitative approach. Under a qualitative approach, the Company considers various market factors, including applicable key assumptions also used in the quantitative assessment listed below. These factors are analyzed to determine if events and circumstances could reasonably have affected the fair value of goodwill and indefinite-lived intangible assets. If the Company determines that it is more likely than not that an indefinite-lived intangible asset or reporting unit goodwill is impaired, the quantitative approach is used to assess the asset or reporting unit fair value and the amount of the impairment. Under a quantitative approach, the fair value of the Company's indefinite-lived intangible asset or reporting unit is calculated based on key market participant assumptions. If the indefinite-lived intangible assets' carrying value exceeds the fair value calculated using the quantitative approach, an impairment charge is recorded for the difference in fair value and carrying value. If the reporting unit carrying value exceeds the reporting unit fair value calculated using the quantitative approach, an impairment charge is recorded for the difference between fair value and carrying value, limited to the amount of goodwill in the reporting unit. When performing a quantitative impairment assessment of goodwill and indefinite-lived intangible assets, fair value is estimated based on (i) recent market transactions, where available, (ii) projected discounted cash flows (an income approach), or (iii) a combination of limited market transactions and the lease savings method (which reflects potential annual after-tax lease savings arising from owning the certain indefinite-lived intangibles rather than leasing them from another airline at market rates). The Company applied the quantitative approach during its annual 2020 impairment tests. Key assumptions and/or estimates made in the Company's 2020 impairment tests included the following: (i) a projection of revenues, expenses, and cash flows; (ii) terminal period revenue growth and cash flows; (iii) an estimated weighted average cost of capital; (iv) an assumed discount rate depending on the asset; (v) a tax rate; and (vi) market purchase prices and lease rates for comparable assets. The Company believes these assumptions are consistent with those a hypothetical market participant would use given circumstances that were present at the time the estimates were made. However, actual results and amounts may be significantly different from the Company's estimates. As a result of the annual impairment tests performed as of October 1, 2020, no impairment was determined to exist for Goodwill or indefinite-lived intangible assets, as the fair values of the reporting unit and indefinite-lived intangible assets exceeded their respective carrying values. The Company’s intangible assets primarily consist of acquired rights to certain airport owned takeoff and landing slots (a "slot" is the right of an air carrier, pursuant to regulations of the Federal Aviation Administration ("FAA"), to operate a takeoff or landing at a specific time at certain airports) at certain domestic slot-controlled airports. Indefinite lived slots of $295 million are included as a component of Other assets in the Company's Consolidated Balance Sheet, as of December 31, 2020 and 2019. Revenue Recognition Tickets sold are initially deferred as Air traffic liability. Passenger revenue is recognized and Air traffic liability is reduced when transportation is provided. Air traffic liability primarily represents tickets sold for future travel dates, funds that are past flight date and remain unused, but are expected to be used in the future, and the Company’s liability for loyalty benefits that are expected to be redeemed in the future. The majority of the Company’s tickets sold are nonrefundable. Southwest has a No Show policy that applies to fares that are not canceled or changed by a Customer at least ten minutes prior to a flight's scheduled departure. Nonrefundable tickets that are sold but not flown on the travel date, and are canceled in accordance with the No Show policy, can be applied to future travel. Refundable tickets that are sold but not flown on the travel date can also be applied to future travel. A small percentage of tickets (or partial tickets) expire unused. The Company estimates the amount of tickets that expire unused and recognizes such amounts in Passenger revenue once the scheduled flight date has lapsed in proportion to the pattern of flights taken by the Customers. Based on the Company's revenue recognition policy, revenue is recorded at the flight date for a Customer who does not change his/her itinerary and loses his/her funds as the Company has then fulfilled its performance obligation. Amounts collected from passengers for ancillary services are also recognized when the service is provided, which is typically the flight date. Initial spoilage estimates for both tickets and funds available for future use are routinely adjusted and ultimately finalized once the tickets expire, which is typically twelve months after the original purchase date. However, during 2020, the Company extended the expiration dates for a significant amount of tickets and funds beyond its normal twelve months. Spoilage estimates are based on the Company's Customers' historical travel behavior as well as assumptions about the Customers' future travel behavior. Assumptions used to generate spoilage estimates can be impacted by several factors including, but not limited to: fare increases, fare sales, changes to the Company's ticketing policies, changes to the Company’s refund, exchange, and unused funds policies, seat availability, and economic factors. Given the unprecedented amount of 2020 Customer flight cancellations and the amount of travel funds provided, the Company expects additional variability in the amount of spoilage revenue recorded in future periods, as the estimates of the portion of sold tickets that will expire unused may differ from historical experience. See Note 6 for further information. Approximately $184 million, approximately $615 million, and approximately $566 million of the Company's Operating revenues in 2020, 2019, and 2018, respectively, were attributable to foreign operations. The remainder of the Company's Operating revenues, approximately $8.9 billion, approximately $21.8 billion, and approximately $21.4 billion in 2020, 2019, and 2018, respectively, were attributable to domestic operations. Loyalty Program The Company records a liability for the relative fair value of providing free travel under its loyalty program for all points earned from flight activity or sold to companies participating in the Company’s Rapid Rewards loyalty program as business partners that are expected to be redeemed for future travel. The loyalty liability represents performance obligations that will be satisfied when a Rapid Rewards loyalty member redeems points for travel or other goods and services. Points earned from flight activity are valued at their relative standalone selling price by applying fair value based on historical redemption patterns. Points earned from business partner activity, which primarily consist of points sold, along with related marketing services, to companies participating in the Rapid Rewards loyalty program, are valued using a relative fair value methodology based on the contractual rate which partners pay to Southwest to award Rapid Rewards points to the business partner’s customers. For points that are expected to remain unused, the Company recognizes spoilage in proportion to the pattern of points used by the Customer, which approximates the average period over which the population of Rapid Reward Members redeem their points. The Company records passenger revenue related to air transportation when the transportation is delivered. The marketing elements are recognized as Other - net revenue when earned. The Company’s liability for loyalty benefits includes a portion that is expected to be redeemed during the following twelve months (classified as a component of Air traffic liability), and a portion that is not expected to be redeemed during the following twelve months (classified as Air traffic liability - noncurrent). The Company continually updates this analysis and adjusts the split between current and non-current liabilities as appropriate. See Note 6 for further information. Advertising Advertising costs are charged to expense as incurred. Advertising and promotions expense for the years ended December 31, 2020, 2019, and 2018 was $156 million, $212 million, and $215 million, respectively, and is included as a component of Other operating expense in the accompanying Consolidated Statement of Income (Loss). Share-based Employee Compensation The Company has share-based compensation plans covering certain Employees, including a plan that also covers the Company’s Board of Directors. The Company accounts for share-based compensation based on its grant date fair value. See Note 10 for further information. Financial Derivative Instruments The Company accounts for financial derivative instruments at fair value and applies hedge accounting rules where appropriate. The Company utilizes various derivative instruments, including jet fuel, crude oil, unleaded gasoline, and heating oil-based derivatives, to attempt to reduce the risk of its exposure to jet fuel price increases. These instruments are accounted for as cash flow hedges upon proper qualification. The Company also has had interest rate swap agreements to convert certain floating-rate debt to a fixed-rate and had interest rate swap agreements to convert portions of its fixed-rate debt to floating rates. The Company has forward-stating interest rate swap agreements, the primary objective of which is to hedge forecasted debt issuances. These interest rate hedges are appropriately designated as cash flow hedges. Since the majority of the Company’s financial derivative instruments are not traded on a market exchange, the Company estimates their fair values. Depending on the type of instrument, the values are determined by the use of present value methods or option value models with assumptions about commodity prices based on those observed in underlying markets. All cash flows associated with purchasing and selling derivatives are classified as operating cash flows in the Consolidated Statement of Cash Flows, within Changes in certain assets and liabilities. The Company classifies its cash collateral provided to or held from counterparties in a "net" presentation on the Consolidated Balance Sheet against the fair value of the derivative positions with those counterparties. See Note 11 for further information. Software Capitalization The Company capitalizes certain internal and external costs related to the acquisition and development of internal use software during the application development stages of projects. The Company amortizes these costs using the straight-line method over the estimated useful life of the software, which is typically five Insurance Reserves The Company uses a combination of insurance and self-insurance mechanisms, including a wholly-owned captive insurance entity and participation in a reinsurance treaty, to provide for the potential liabilities associated with certain risks, including workers’ compensation, healthcare benefits, general liability, and aviation liability. Liabilities associated with the risks that are retained by the Company are not discounted and are estimated, in part, by considering historical claims experience, demographics, exposure and severity factors and other actuarial assumptions. Income Taxes The Company accounts for deferred income taxes utilizing an asset and liability method, whereby deferred tax assets and liabilities are recognized based on the tax effect of temporary differences between the financial statements and the tax basis of assets and liabilities, as measured by current enacted tax rates. The Company also evaluates the need for a valuation allowance to reduce deferred tax assets to estimated recoverable amounts. The Company’s policy for recording interest and penalties associated with uncertain tax positions is to record such items as a component of Income (loss) before income taxes. Penalties are recorded in Other (gains) losses, net, and interest paid or received is recorded in Interest expense or Interest income, respectively, in the accompanying Consolidated Statement of Income (Loss). There were no material amounts recorded for penalties and interest related to uncertain tax positions for all years presented. See Note 15 for further information. Concentration Risk Approximately 83 percent of the Company’s full-time equivalent Employees are unionized and are covered by collective-bargaining agreements. A percentage of the Company's unionized Employees, including its Pilots, Flight Attendants, Customer Service Agents, Dispatchers, Aircraft Appearance Technicians, and Meteorologists, which had contracts that became amendable on or before December 31, 2020, are in discussions on labor agreements. Those unionized Employee groups in discussions represent approximately 55 percent of the Company’s full-time equivalent Employees as of December 31, 2020. The Company attempts to minimize its concentration risk with regards to its cash, cash equivalents, and its investment portfolio. This is accomplished by diversifying and limiting amounts among different counterparties, the type of investment, and the amount invested in any individual security or money market fund. To manage risk associated with financial derivative instruments held, the Company selects and will periodically review counterparties based on credit ratings, limits its exposure to a single counterparty, and monitors the market position of the program and its relative market position with each counterparty. The Company also has agreements with counterparties containing early termination rights and/or bilateral collateral provisions whereby security is required if market risk exposure exceeds a specified threshold amount or credit ratings fall below certain levels. Collateral deposits provided to or held from counterparties serve to decrease, but not totally eliminate, the credit risk associated with the Company’s hedging program. See Note 11 for further information. As of December 31, 2020, the Company operated an all-Boeing fleet, all of which are variations of the Boeing 737. The Boeing 737 MAX aircraft ("MAX") are crucial to the Company’s growth plans and fleet modernization initiatives. On March 13, 2019, the FAA issued an emergency order for all U.S. airlines to ground the MAX aircraft, including the 34 MAX aircraft in the Company's fleet. On November 18, 2020, the FAA rescinded its order to ground the MAX fleet. The Company is currently working to meet the FAA's requirements by modifying certain operating procedures, implementing enhanced Pilot training requirements, installing FAA-approved flight control software updates, and completing other required maintenance tasks specific to the MAX aircraft. The Company currently estimates that the MAX will return to service on March 11, 2021 after all active Pilots have received updated, MAX-related training. The MAX fleet grounding has adversely affected the Company's operating results, and could have a material adverse effect on the Company's operating results in future periods. Boeing no longer manufactures versions of the 737 other than the 737 MAX family of aircraft. If the 737 MAX aircraft were to again become unavailable for the Company’s flight operations, the Company’s growth would be restricted unless and until it could procure and operate other types of aircraft from Boeing or another manufacturer, seller, or lessor, and the Company’s operations would be materially adversely affected. In particular, if the Company’s growth were to be dependent upon the introduction of a new aircraft make and model to the Company’s fleet, the Company would need to, among other things, (i) develop and implement new maintenance, operating, and training programs, (ii) secure extensive regulatory approvals, and (iii) implement new technologies. The requirements associated with operating a new aircraft make and model could take an extended period of time to fulfill and would likely impose substantial costs on the Company. A shift away from a single fleet type could also add complexity to the Company’s operations, present operational and compliance risks, and materially increase the Company's costs. Any of these events would have a material, adverse effect on the Company's business, operating results, and financial condition. The Company could also be materially adversely affected if the pricing or operational attributes of its aircraft were to become less competitive. See Note 17 for further information. The Company is also dependent on sole or limited suppliers for aircraft engines and certain other aircraft parts and services and would, therefore, also be materially adversely impacted in the event of the unavailability of, inadequate support for, or a mechanical or regulatory issue associated with, engines and other parts. The Company has historically entered into agreements with some of its co-brand, payment, and loyalty partners that contain exclusivity aspects which place certain confidential restrictions on the Company from entering into certain arrangements with other payment and loyalty partners. Some of these agreements automatically renew on an annual basis, unless either party objects to such extension. None of these agreements are more than 10 years in length. The Company believes the financial benefits generated by the exclusivity aspects of these arrangements outweigh the risks involved with such agreements.

WORLDWIDE PANDEMIC

WORLDWIDE PANDEMIC	12 Months Ended
	Dec. 31, 2020
Worldwide Pandemic [Abstract]
Worldwide Pandemic	WORLDWIDE PANDEMICAs a result of the rapid spread of the novel coronavirus, COVID-19, throughout the world, including into the United States, on March 11, 2020, the World Health Organization classified the virus as a pandemic. The speed with which the effects of the COVID-19 pandemic have changed the U.S. economic landscape, outlook, and in particular the travel industry, were swift and unexpected. The Company began to see a negative impact on bookings for future travel in late February 2020, which quickly accelerated during the remainder of first quarter and into second quarter, when trip cancellations outpaced new passenger bookings during the majority of March and April 2020. The Company began proactively canceling a significant portion of its scheduled flights in March 2020, and continued adjusting capacity throughout the remainder of the year, as the Company grounded a significant portion of its fleet and operated a significantly reduced portion of its previously scheduled capacity. The Company continued to experience significant negative impacts to passenger demand and bookings through the remainder of 2020 due to the pandemic. Based on these events and the uncertainty they created, the Company immediately began to focus on its liquidity, including quickly and substantially enhancing its cash holdings. Throughout 2020, the Company raised a total of $18.9 billion in capital, net of transaction fees. On April 20, 2020, the Company entered into definitive documentation with the United States Department of Treasury (the "Treasury") with respect to funding support pursuant to the Payroll Support Program ("Payroll Support") under the Coronavirus Aid, Relief and Economic Security Act ("CARES Act"). During 2020, the Company received a total of $3.4 billion of relief funds under the CARES Act. As consideration for the Payroll Support, the Company issued a promissory note (the "Note") in favor of the Treasury and entered into a warrant agreement with the Treasury (the "Warrant Agreement"), pursuant to which the Company agreed to issue warrants (each, a "Warrant") to purchase common stock of the Company to the Treasury. During 2020, the Company provided a Note in the aggregate amount of $976 million and issued Warrants valued at a total of $40 million to purchase up to an aggregate of 2.7 million shares of the Company's common stock, subject to adjustment pursuant to the terms of the Warrants. Pursuant to the terms of the Payroll Support Program agreement and the CARES Act, the Payroll Support funds could only be utilized to pay qualifying salaries, wages, and benefits, as defined in the CARES Act. As of December 31, 2020, excluding the $976 million Note and value allocated to the Warrants, all Payroll Support funds received have been allocated to reduce eligible costs in the accompanying Consolidated Statement of Comprehensive Income (Loss) for the year ended December 31, 2020. The Note matures in full on April 19, 2030, and is subject to mandatory prepayment requirements in connection with certain change of control triggering events that may occur prior to its maturity. The Company has an option to prepay the Note at any time without premium or penalty. Amounts outstanding under the Note bear interest at a rate of 1.00 percent before April 20, 2025 and, afterwards, at a rate equal to the Secured Overnight Financing Rate or other benchmark replacement rate consistent with customary market conventions plus a margin of 2.00 percent. The Note contains customary representations and warranties and events of default. Also under the Cares Act terms, as supplemented by the Payroll Support Program Extension (discussed below), the Company is prohibited from repurchasing its common stock and from paying dividends or making capital contributions with respect to its common stock through March 31, 2022. The Warrant Agreement sets out the Company’s obligations to issue Warrants in connection with disbursements of Payroll Support and to file a resale shelf registration statement for the Warrants and the underlying shares of common stock. The Company has also granted the Treasury certain demand underwritten offering and piggyback registration rights with respect to the Warrants and the underlying common stock. Each Warrant is exercisable at a strike price of $36.47 per share of common stock and will expire on the fifth anniversary of the issue date of such Warrant. The Warrants will be settled through net share settlement or net cash settlement, at the Company’s option. The Warrants include adjustments for below market issuances, payment of dividends, and other customary anti-dilution provisions. The Warrants do not have voting rights. In addition to obtaining financing under the CARES Act and accessing the capital markets, the Company believes it has made significant progress on bolstering its liquidity through efforts including aggressively evaluating all capital spending, discretionary spending, and non-essential costs for near-term cost reductions or deferrals; reducing the Company's published flight schedule; placing a significant number of aircraft in storage; implementing voluntary separation and time-off programs for Employees; substantially suspending all hiring; reducing the Chief Executive Officer's salary by 20 percent; reducing the other named executive officer salaries and Board of Director cash retainer fees by 20 percent through December 31, 2020; and modifying vendor and supplier payment terms. The Company will continue evaluating the need for further flight schedule adjustments. On December 27, 2020, President Trump signed into law the Consolidated Appropriations Act, 2021 (the "Payroll Support Program Extension"). Among other items, this Payroll Support Program Extension will provide up to an additional $15 billion in support to U.S. airlines through payroll support grants as well as loans that will require repayment to the U.S. government. During January 2021, the Company completed its application for such additional support, and finalized an agreement with the Treasury in which it will receive approximately $1.7 billion in funds that will be used to pay qualifying Employee wages and benefits through at least March 31, 2021. The Company received an initial installment of $864 million in January 2021, and expects to receive the remainder of funds during first quarter 2021. As consideration for the payroll support received in January 2021, the Company issued a promissory note in favor of the Treasury and entered into a warrant agreement with the Treasury, pursuant to which the Company agreed to issue warrants to purchase common stock of the Company to the Treasury. The promissory note was issued for $229 million and warrants were valued at a total of $9 million to purchase up to an aggregate of 495 thousand shares of the Company's common stock, subject to adjustment pursuant to the terms of the warrants. Once the second installment is received, the Company will issue the remaining $259 million promissory note and warrants to purchase up to an additional 560 thousand shares of the Company's common stock. The funds received during 2021 can only be utilized to pay qualifying salaries, wages, and benefits, as defined. Excluding the amounts allocated to the promissory note and value allocated to the Warrants, all funds received during 2021 are expected to be allocated to reduce eligible costs in the year ended December 31, 2021. On June 1, 2020, the Company announced Voluntary Separation Program 2020, a voluntary separation program that allowed eligible Employees the opportunity to voluntarily separate from the Company in exchange for severance, medical/dental coverage for a specified period of time, and travel privileges based on years of service. Virtually all of the Company’s Employees hired before June 1, 2020 were eligible to participate in Voluntary Separation Program 2020. A total of over 4,200 Employees elected to participate in Voluntary Separation Program 2020, consisting of the following breakdown among workgroups: 1,060 from Ground Operations and Provisioning, 725 Flight Attendants, 630 Pilots, 390 from Customer Support and Services, 185 from Maintenance, 90 from other Contract groups, and 1,140 Managerial and Administrative Employees. Voluntary Separation Program 2020 participants’ last day of work primarily fell between August 15, 2020 and September 30, 2020, as assigned by the Company based on the operational needs of particular work locations and departments, determined on an individual-by-individual basis. In conjunction with Voluntary Separation Program 2020, the Company also offered certain contract Employees the option to take voluntary Extended Emergency Time Off ("Extended ETO"), for periods between six The purpose of Voluntary Separation Program 2020 and Extended ETO is to maintain a suitable sized workforce to operate at reduced capacity relative to the Company's operations prior to the COVID-19 pandemic. In accordance with the accounting guidance in ASC Topic 712 (Compensation — Nonretirement Postemployment Benefits), the Company accrued charges related to the special termination benefits described above upon Employees accepting Voluntary Separation Program 2020 or Extended ETO offers, which will be reduced as program benefits are paid. Costs incurred for Voluntary Separation Program 2020 and Extended ETO, which totaled $1.4 billion throughout 2020, are recorded as a component of Payroll support and voluntary Employee programs, net, in the accompanying Consolidated Statement of Comprehensive Income (Loss). Within that line item, these charges are netted against the allocation of the remainder of the Payroll Support Program funds utilized to fund salaries, wages, and benefits, which totaled $2.3 billion throughout 2020. The Company accrued expenses totaling $620 million for its Extended ETO program throughout 2020, consisting of future wages and benefits for the Employees that will not be working. The Company has accrued amounts up to 18 months for all Employees that elected Extended ETO, but did not include amounts related to Pilots for periods beyond February 2022, based on the uncertainty of its future capacity levels, and because it is not currently probable that such Employees will not be recalled to work beyond that timeframe. Therefore, future adjustments to the amounts accrued as of December 31, 2020, may become necessary at a later date. For both the Voluntary Support Program 2020 and Extended ETO programs combined, approximately $454 million of the liability balances were relieved during 2020 (primarily through payments to Employees), leaving a balance of $914 million as of December 31, 2020. In response to flight schedule adjustments due to the effects of the COVID-19 pandemic, a number of aircraft were taken out of the Company’s schedule beginning in late March, and placed in short-term storage, as well as some in a longer term storage program. In addition, during fourth quarter 2020, the Company made the decision to permanently retire 20 of its older 737-700 aircraft, given the expected return to service of the Company's Boeing MAX 737 aircraft on March 11, 2021. The early retirement of these 20 737-700s resulted in an impairment charge of $32 million in 2020, which is classified within Other operating expenses in the Consolidated Statement of Income (Loss). As of December 31, 2020, 92 aircraft remained in temporary storage. Given the current expectation that these aircraft have been placed in storage temporarily, the Company has continued to record depreciation expense associated with them. As a result of the events and impacts surrounding the COVID-19 pandemic, including the Company's net loss incurred during the year ended December 31, 2020, and the significant number of aircraft that have been placed in storage, the Company considered whether these conditions indicated that it was more likely than not that the Company’s $970 million in Goodwill and its $295 million in indefinite-lived intangible assets were impaired. As a result of the annual impairment tests performed as of October 1, 2020, no impairment was determined to exist for Goodwill or indefinite-lived intangible assets, See Note 1 for further information. In addition, the Company has assessed whether any impairment of its amortizable assets existed, and has determined that no charges were deemed necessary under applicable accounting standards as of December 31, 2020. The Company’s assumptions about future conditions important to its assessment of potential impairment of its amortizable assets, indefinite-lived intangible assets, and Goodwill, including the impacts of the COVID-19 pandemic and other ongoing impacts to its business, are subject to uncertainty, and the Company will continue to monitor these conditions in future periods as new information becomes available, and will update its analyses accordingly.

NEW ACCOUNTING PRONOUNCEMENTS

NEW ACCOUNTING PRONOUNCEMENTS	12 Months Ended
	Dec. 31, 2020
Accounting Changes and Error Corrections [Abstract]
NEW ACCOUNTING PRONOUNCEMENTS	NEW ACCOUNTING PRONOUNCEMENTS AND ACCOUNTING CHANGES On August 5, 2020, the Financial Accounting Standards Board (the "FASB") issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity. This new standard reduces the number of accounting models for convertible debt instruments and convertible preferred stock, enhances information transparency by making targeted improvements to the disclosures for convertible instruments and earnings-per-share (EPS) guidance, and amends the guidance for the derivatives scope exception for contracts in an entity’s own equity to reduce form-over-substance-based accounting conclusions. This standard is effective for fiscal years beginning after December 15, 2021. Companies may elect early adoption for periods beginning after December 15, 2020. The FASB specified that an entity should adopt the guidance as of the beginning of its annual fiscal year. The Company is evaluating this new standard and plans to provide additional information about its expected impact on the Company's financial statements and disclosures at a future date. On December 18, 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. This new standard eliminates certain exceptions in ASC 740 related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period, and the recognition of deferred tax liabilities for outside basis differences. It also clarifies and simplifies other aspects of the accounting for income taxes. This standard is effective for fiscal years, and interim periods within those years, beginning after December 15, 2020, with early adoption permitted in any interim period within that year. The Company elected to early adopt this standard as of January 1, 2020. The most significant impact to the Company is the removal of a limit on the tax benefit recognized on pre-tax losses in interim periods. However, the early adoption as of January 1, 2020, did not have an impact on the Company's financial statements or disclosures for 2020. On August 29, 2018, the FASB issued ASU No. 2018-15, Intangibles—Goodwill and Other—Internal-Use Software. This standard requires a customer in a cloud computing arrangement that is a service contract to follow the internal-use software guidance in ASC 350-40, Accounting for Internal-Use Software, to determine which implementation costs to (i) capitalize as assets and amortize over the term of the hosting arrangement or (ii) expense as incurred. This standard is effective for public business entities in fiscal years beginning after December 15, 2019, and the standard was adopted and applied prospectively by the Company as of January 1, 2020, but it did not have a significant impact on the Company's financial statements and disclosures. On August 28, 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement. This standard is effective for public business entities in fiscal years beginning after December 15, 2019, and for interim periods within those fiscal years. This standard requires changes to the disclosure requirements for fair value measurements for certain Level 3 items, and specifies that some of the changes must be applied prospectively, while others should be applied retrospectively. The Company adopted the standard as of January 1, 2020, but it did not have a significant impact on the Company's financial statements or disclosures. See Note 12 for further information on the Company's fair value measurements. On January 26, 2017, the FASB issued ASU No. 2017-04, Simplifying the Test for Goodwill Impairment. The new standard eliminates Step 2 from the goodwill impairment test. An entity should recognize a goodwill impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value. This standard is effective for public business entities in fiscal years beginning after December 15, 2019, and the standard was adopted and applied prospectively by the Company as of January 1, 2020, but it did not have a significant impact on the Company's financial statements and disclosures. On June 16, 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments. The new standard requires the use of an “expected loss” model on certain types of financial instruments. The standard also amends the impairment model for available-for-sale debt securities and requires estimated credit losses to be recorded as allowances instead of reductions to amortized cost of the securities. This standard is effective for public business entities in fiscal years beginning after December 15, 2019, and the standard was adopted and applied prospectively by the Company as of January 1, 2020, but it did not have a significant impact on the Company's financial statements and disclosures. On February 25, 2016, the FASB issued the New Lease Standard. The New Lease Standard requires lessees to recognize a right-of-use asset and a lease liability on the balance sheet for all leases (with the exception of short-term leases, as defined in the New Lease Standard) at the lease commencement date and recognize expenses on the income statement in a similar manner to the legacy guidance in ASC 840, Leases ("ASC 840"). The Company adopted the provisions of the New Lease Standard effective January 1, 2019, using the modified retrospective adoption method, utilizing the simplified transition option available in the New Lease Standard, which allows entities to continue to apply the legacy guidance in ASC 840, including its disclosure requirements, in the comparative periods presented in the year of adoption. The Company elected the package of practical expedients available under the transition provisions of the New Lease Standard, including (i) not reassessing whether expired or existing contracts contain leases, (ii) not reassessing lease classification, and (iii) not revaluing initial direct costs for existing leases.

NET INCOME (LOSS) PER SHARE

NET INCOME (LOSS) PER SHARE	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
NET INCOME (LOSS) PER SHARE	NET INCOME (LOSS) PER SHARE The following table sets forth the computation of basic and diluted net income (loss) per share (in millions except per share amounts). An immaterial number of shares related to the Company's restricted stock units, stock warrants, and convertible notes were excluded from the denominator for fiscal year ended December 31, 2020, because inclusion of such shares would be antidilutive. Year ended December 31, 2020 2019 2018 NUMERATOR: Net income (loss) $ (3,074) $ 2,300 $ 2,465 DENOMINATOR: Weighted-average shares outstanding, basic 565 538 573 Dilutive effect of restricted stock units — 1 1 Adjusted weighted-average shares outstanding, diluted 565 539 574 NET INCOME (LOSS) PER SHARE: Basic $ (5.44) $ 4.28 $ 4.30 Diluted $ (5.44) $ 4.27 $ 4.29

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Commitments The Company has contractual obligations and commitments primarily with regard to future purchases of aircraft, repayment of debt (see Note 7), and lease arrangements (see Note 8). During the year ended December 31, 2020, the Company leased seven new Boeing 737 MAX 8 aircraft. The Company expects to lease an additional nine new 737 MAX 8 aircraft in 2021. The Company has firm orders in place with Boeing for 219 737 MAX 8 aircraft and 30 737 MAX 7 aircraft, as well as options for 115 737 MAX 8 aircraft as of December 31, 2020. The Company's 34 Boeing 737 MAX 8 aircraft were previously grounded on March 13, 2019, upon the FAA emergency order for all U.S. airlines to ground all MAX aircraft. On November 18, 2020, the FAA rescinded the emergency order and issued official requirements to enable airlines to return the 737 MAX to service. See Note 17 for further information. All MAX deliveries that should have occurred in 2019 and 2020 based on the Company's existing commitment contract with Boeing have been assumed to shift into future periods. However, the Company reached an agreement with The Boeing Company (the "Boeing Agreement") in December 2020, for the Company to begin to take delivery of the delayed MAX aircraft, with the expectation that the Company will take delivery of 35 MAX 8 aircraft, including the 16 leased aircraft discussed above, through the end of 2021, and that the parties expect to formally revise the existing purchase agreement in 2021 for future deliveries. Based on the Company's current contract with Boeing (prior to the recent Boeing Agreement), capital commitments associated with its firm orders are as follows: $1.7 billion in 2021, $1.2 billion in 2022, $1.6 billion in 2023, $1.9 billion in 2024, and $1.5 billion in 2025. In addition, the capital commitments associated with the contractual MAX deliveries that did not take place in 2019 and 2020, which are assumed to shift to future periods, total $2.1 billion ($743 million from 2019 and $1.3 billion from 2020). However, based on the Boeing Agreement, the Company is expected to take no more than 19 purchased MAX aircraft through December 31, 2021. The Boeing Agreement also stipulated a confidential settlement for estimated financial damages incurred by the Company in 2020 as a result of the MAX grounding, in the form of credits that can be taken against future payments due to Boeing. With respect to the 19 expected purchased MAX deliveries, considering contractual progress payments that have been made to Boeing and expected credits from Boeing, the Company expects its actual aircraft capital expenditures during 2021 to be immaterial. The Company is continuing discussions with Boeing to refresh its order book and the timeline of future deliveries is uncertain. Los Angeles International Airport In October 2017, the Company executed a lease agreement with Los Angeles World Airports ("LAWA") (the "T1.5 Lease"). Under the T1.5 Lease, the Company oversaw and managed the design, development, financing, construction, and commissioning of a passenger processing facility between Terminal 1 and 2 (the "Terminal 1.5 Project"). The Terminal 1.5 Project includes ticketing, baggage claim, passenger screening, and a bus gate at a cost not to exceed $464 million for site improvements and non-proprietary improvements. Construction on the Terminal 1.5 Project began during third quarter 2017 and was substantially completed at December 31, 2020; however, the Terminal 1.5 Project will not be placed into service until second quarter 2021, at which time LAWA is expected to repay the outstanding loan and purchase the remaining completed assets for accounting purposes. The costs incurred to fund the Terminal 1.5 Project are included within Assets Constructed for Others ("ACFO") and all amounts that have been or will be reimbursed will be included within Construction obligation on the accompanying Consolidated Balance Sheet. Upon completion of any individual asset as part of the overall project, the asset and associated liability on the balance sheet are de-recognized in accordance with applicable accounting guidance. Funding for this project is primarily through the Regional Airports Improvement Corporation (the "RAIC"), which is a quasi-governmental special purpose entity that is acting as a conduit borrower under a syndicated credit facility provided by a group of lenders. A loan made under the credit facility for the Terminal 1.5 Project is being used to reimburse the Company for the site improvements and non-proprietary improvements of the Terminal 1.5 Project, and the outstanding loan will be repaid with the proceeds of LAWA’s payments to purchase completed construction phases. The Company guaranteed the obligation of the RAIC under the credit facility associated with the Terminal 1.5 Project. As of December 31, 2020, the Company's outstanding guaranteed obligation under the credit facility for the Terminal 1.5 Project was $318 million. Construction costs recorded in ACFO for the Terminal 1.5 Project, which exclude costs associated with assets that were previously completed and placed into service, were $309 million and $164 million, as of December 31, 2020, and December 31, 2019, respectively. Dallas Love Field During 2008, the City of Dallas approved the LFMP, a project to reconstruct Dallas Love Field with modern, convenient air travel facilities. Pursuant to a Program Development Agreement with the City of Dallas and the Love Field Airport Modernization Corporation (or the "LFAMC," a Texas non-profit "local government corporation" established by the City of Dallas to act on the City of Dallas' behalf to facilitate the development of the LFMP), the Company managed this project. Major construction was effectively completed in 2014. During second quarter 2017, the City of Dallas approved using the remaining bond funds for additional terminal construction projects, which were effectively completed in 2018. Although the City of Dallas received commitments from various sources that helped to fund portions of the LFMP project, including the FAA, the Transportation Security Administration, and the City of Dallas' Aviation Fund, the majority of the funds used were from the issuance of bonds. The Company guaranteed principal and interest payments on bonds issued by the LFAMC. As of December 31, 2020, $399 million of principal remained outstanding. The net present value of the future principal and interest payments associated with the bonds were $433 million and $444 million as of December 31, 2020 and December 31, 2019, respectively, and was reflected as part of the Company's operating lease right-of-use assets and lease obligations in the Consolidated Balance Sheet. Contingencies The Company is from time to time subject to various legal proceedings and claims arising in the ordinary course of business, including, but not limited to, examinations by the Internal Revenue Service ("IRS"). The Company's management does not expect that the outcome of any of its currently ongoing legal proceedings or the outcome of any adjustments presented by the IRS, individually or collectively, will have a material adverse effect on the Company's financial condition, results of operations, or cash flow.

REVENUE

REVENUE	12 Months Ended
	Dec. 31, 2020
Revenue Recognition and Deferred Revenue [Abstract]
Revenue from Contract with Customer	REVENUE Passenger Revenues The Company’s contracts with its Customers primarily consist of its tickets sold, which are initially deferred as Air traffic liability. Passenger revenue associated with tickets is recognized when the performance obligation to the Customer is satisfied, which is primarily when travel is provided. Revenue is categorized by revenue source as the Company believes it best depicts the nature, amount, timing, and uncertainty of revenue and cash flow. The following table provides the components of Passenger revenue recognized for the years ended December 31, 2020, 2019, and 2018: Year ended December 31, (in millions) 2020 2019 2018 Passenger non-loyalty $ 6,303 $ 17,578 $ 17,506 Passenger loyalty - air transportation 1,003 2,487 2,307 Passenger ancillary sold separately 359 711 642 Total passenger revenues $ 7,665 $ 20,776 $ 20,455 Passenger non-loyalty includes all revenues recognized from Passengers related to flights paid for primarily with cash or credit card. All Customers purchasing a ticket on Southwest Airlines are generally able to check up to two bags at no extra charge (with certain exceptions as stated in the Company's published Contract of Carriage), and the Company also does not charge a fee for a Customer to make a change to their flight after initial purchase, although fare differences may apply. Passenger loyalty - air transportation primarily consists of the revenue recognized associated with award flights taken by loyalty program members upon redemption of loyalty points. Passenger ancillary sold separately includes any revenue recognized associated with ancillary fees charged separately, such as in-flight purchases, EarlyBird Check-In ® , and Upgraded Boarding. In order to determine the value of each loyalty point, certain assumptions must be made at the time of measurement, which include the following: • Allocation of Passenger Revenue - Revenues from Passengers, related to travel, who also earn Rapid Rewards Points have been allocated between flight (recognized as revenue when transportation is provided) and Rapid Rewards Points (deferred until points are redeemed) based on each obligation’s relative standalone selling price. The Company utilizes historical earning patterns to assist in this allocation. • Fair Value of Rapid Rewards Points - Determined from the base fare value of tickets which were purchased using prior point redemptions for travel and other products and services, which the Company believes to be indicative of the fair value of points as perceived by Customers and representative of the value of each point at the time of redemption. The Company’s booking site allows a Customer to toggle between fares utilizing either cash or point redemptions, which provides the Customer with an approximation of the equivalent value of their points. The value can differ, however, based on demand, the amount of time prior to the flight, and other factors. The fare mix during the period measured represents a constraint, which could result in the assumptions above changing at the measurement date, as fare classes can have different coefficients used to determine the total loyalty points needed to purchase an award ticket. The mixture of these fare classes and changes in the coefficients used by the Company could cause the fair value per point to increase or decrease. For points that are expected to remain unused, the Company recognizes spoilage in proportion to the pattern of points used by the Customer, which approximates the average period over which the population of Rapid Reward Members redeem their points. The Company utilizes historical behavioral data to develop a predictive statistical model to analyze the amount of spoilage expected for points sold to business partners and earned through flight. The Company continues to evaluate expected spoilage annually and applies appropriate adjustments in the fourth quarter of each year, or other times, if changes in Customer behavior are detected. Changes to spoilage estimates impact revenue recognition prospectively. Due to the size of the Company’s liability for loyalty benefits, changes in Customer behavior and/or expected future redemption patterns could result in significant variations in Passenger revenue. The Company allocates consideration received to performance obligations based on the relative fair value of those obligations. The Company has a co-branded credit card agreement (“Agreement”) with Chase Bank USA, N.A. (“Chase”), through which the Company sells loyalty points and certain marketing components, which consist of the use of the Southwest Airlines brand and access to Rapid Rewards Member lists, licensing and advertising elements, and the use of the Company’s resource team. In 2018, Chase and the Company executed a multi-year extension of the Agreement, extending the decades-long relationship between the parties. The Company estimated the selling prices and volumes over the term of the Agreement in order to determine the allocation of proceeds to each of the two performance obligations identified in the Agreement, which have been characterized as a transportation component and a marketing component. The allocations utilized are reviewed to determine if adjustment is necessary any time there is a modification to the Agreement. The Company records Passenger revenue related to loyalty point redemptions for air travel when the travel is delivered, and the marketing elements are recognized as Other revenue when the performance obligations related to those services are satisfied, which is generally the same period consideration is received from Chase. As performance obligations to Customers are satisfied, the related revenue is recognized. The events that result in revenue recognition that are associated with performance obligations identified as a part of the Rapid Rewards Program are as follows: • Tickets and Rapid Rewards Points - When a flight occurs, the related performance obligation is satisfied and the related value provided by the Customer, whether from purchased tickets or Rapid Rewards Points, is recognized as revenue. • Loyalty points redeemed for goods and/or services other than travel - Rapid Rewards Members have the option to redeem points for goods and services offered through a third party vendor, who acts as principal. The performance obligation related to the purchase of these goods and services is satisfied when the good and/or service is delivered to the Customer. • Marketing Royalties - As part of its Agreement with Chase, Southwest provides certain deliverables, including use of the Southwest Airlines’ brand, access to Rapid Rewards Member lists, advertising elements, and the Company’s resource team. These performance obligations are satisfied each month that the Agreement is active. As of the years ended December 31, 2020 and 2019, the components of Air traffic liability, including contract liabilities based on tickets sold, unused funds available to the Customer, and loyalty points available for redemption, net of expected spoilage, within the Consolidated Balance Sheet were as follows: Balance as of (in millions) December 31, 2020 December 31, 2019 Air traffic liability - passenger travel and ancillary passenger services $ 2,686 $ 2,125 Air traffic liability - loyalty program 4,447 3,385 Total Air traffic liability $ 7,133 $ 5,510 The balance in Air traffic liability - passenger travel and ancillary passenger services also includes unused funds that are available for use by Customers and are not currently associated with a ticket, but represent funds effectively refunded and made available for use to purchase a ticket for a flight that occurs prior to their expiration. These funds are typically created as a result of a prior ticket cancellation or exchange. Rollforwards of the Company's Air traffic liability - loyalty program for the years ended December 31, 2020 and 2019 were as follows (in millions): Year ended December 31, 2020 2019 Air traffic liability - loyalty program - beginning balance $ 3,385 $ 3,011 Amounts deferred associated with points awarded 1,958 2,941 Revenue recognized from points redeemed - Passenger (1,003) (2,487) Revenue recognized from points redeemed - Other (60) (80) Unused funds converted to loyalty points 167 — Air traffic liability - loyalty program - ending balance $ 4,447 $ 3,385 Air traffic liability includes consideration received for ticket and loyalty related performance obligations which have not been satisfied as of a given date. Rollforwards of the amounts included in Air traffic liability as of December 31, 2020 and 2019 were as follows (in millions): Air traffic liability Balance at December 31, 2019 $ 5,510 Current period sales (passenger travel, ancillary services, flight loyalty, and partner loyalty) 9,348 Revenue from amounts included in contract liability opening balances (2,317) Revenue from current period sales (5,408) Balance at December 31, 2020 $ 7,133 Air traffic liability Balance at December 31, 2018 $ 5,070 Current period sales (passenger travel, ancillary services, flight loyalty, and partner loyalty) 21,296 Revenue from amounts included in contract liability opening balances (3,816) Revenue from current period sales (17,040) Balance at December 31, 2019 $ 5,510 During 2020, the Company experienced a significantly higher number of Customer-driven flight cancellations as a result of the COVID-19 pandemic. See Note 2 for further information. As a result, the amount of Customer travel funds held by the Company, net of spoilage, that can be redeemed for future travel as of December 31, 2020, far exceeds previous periods and represents approximately 28 percent of the total Air traffic liability balance at December 31, 2020, as compared to approximately 2 percent of the total Air traffic liability balance at December 31, 2019. In order to provide additional flexibility to Customers who hold these funds, the Company has significantly relaxed its previous policies with regards to the time period within which these funds can be redeemed, which is typically twelve months from the original date of purchase. For all Customer travel funds created or scheduled to expire between March 1 and September 7, 2020 associated with flight cancellations, the Company has extended the expiration date to September 7, 2022. At December 31 2020, $2.1 billion of Customer travel funds remain in Air traffic liability with a September 7, 2022 expiration date. The Company does not have sufficient data to accurately predict the timing of performance obligation satisfaction on these funds due to certain constraints including, but not limited to, consumer confidence, economic health, vaccines, and uncertainty regarding customer travel fund redemption patterns for funds that live longer than 12 months as this is unprecedented in Company history. As a result, recognition of these travel funds as flown revenue, refunds, or spoilage revenue will likely be more volatile from period to period compared to past periods. Further, as presented in the above tables, the Company announced in August 2020 that it would allow qualified travel funds to be converted to Rapid Rewards points through December 15, 2020. Despite the possibility that some of these travel funds may be redeemed beyond the following twelve-month period, the Company has continued to classify them as "current" in the accompanying Consolidated Balance Sheet as they remain a demand liability and the Company does not have sufficient data to enable it to accurately estimate the portion that will not be redeemed for travel in the subsequent twelve months. Further, as presented in the above tables, the Company provided a benefit to Rapid Reward members to allow qualified travel funds to be converted to Rapid Rewards points through December 15, 2020. Recognition of revenue associated with the Company’s loyalty liability can be difficult to predict, as the number of award seats available to members is not currently restricted and they could choose to redeem their points at any time that a seat is available. The performance obligations classified as a current liability related to the Company’s loyalty program were estimated based on expected redemptions utilizing historical redemption patterns, and forecasted flight availability, fares, and coefficients. The entire balance classified as Air traffic liability—noncurrent relates to loyalty points that were estimated to be redeemed in periods beyond 12 months following the representative balance sheet date. The Company expects the majority of loyalty points to be redeemed within two years. All performance obligations related to freight services sold are completed within twelve months or less; therefore, the Company has elected to not disclose the amount of the remaining transaction price and its expected timing of recognition for freight shipments. Other revenues primarily consist of marketing royalties associated with the Company’s co-branded Chase ® Visa credit card, but also include commissions and advertising associated with Southwest.com ® . All amounts classified as Other revenues are paid monthly, coinciding with the Company fulfilling its deliverables; therefore, the Company has elected to not disclose the amount of the remaining transaction price and its expected timing of recognition for such services provided. The Company recognized revenue related to the marketing, advertising, and other travel-related benefits of the revenue associated with various loyalty partner agreements including, but not limited to, the Agreement with Chase, within Other operating revenues. For the years ended December 31, 2020, 2019, and 2018 the Company recognized $1.1 billion, $1.3 billion, and $1.1 billion, respectively.

FINANCING ACTIVITIES

FINANCING ACTIVITIES	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Debt Disclosure [Text Block]	(in millions) December 31, 2020 December 31, 2019 737 Aircraft Notes payable through April 2020 $ — $ 20 Term Loan Agreement payable through May 2020 - 5.223% — 134 2.65% Notes due November 2020 — 500 2.75% Notes due 2022 300 300 Pass Through Certificates due 2022 - 6.24% 137 197 4.75% Notes due 2023 1,250 — 1.25% Convertible Notes due 2025 1,945 — 5.25% Notes due 2025 1,550 — Term Loan Agreement payable through 2025 - 1.65% 119 — 3.00% Notes due 2026 300 300 Term Loan Agreement payable through 2026 - 1.34% 159 178 3.45% Notes due 2027 300 300 5.125% Notes due 2027 2,000 — 7.375% Debentures due 2027 119 122 Term Loan Agreement payable through 2028 - 1.65% 184 — 2.625% Notes due 2030 500 — 1.000% Payroll Support Program Loan due 2030 (See Note 2) 976 — Finance leases 542 627 $ 10,381 $ 2,678 Less current maturities 220 819 Less debt discount and issuance costs 50 13 $ 10,111 $ 1,846 AirTran Holdings was party to aircraft purchase financing facilities. Each note was secured by a first mortgage on the aircraft to which it related. The notes bore interest at a floating rate per annum equal to a margin plus the three or six-month LIBOR in effect at the commencement of each semi-annual or three-month period, as applicable. Principal and interest under the notes were payable semi-annually or every three months as applicable. The three remaining notes matured in 2020 (February and April) and were redeemed in full utilizing available cash on hand. As discussed further in Note 11, a portion of the above floating-rate debt had been effectively converted to a fixed rate via interest rate swap agreements which expired as the underlying notes matured. In third quarter 2020, the Company entered into agreements with a financing institution to borrow $125 million ($121 million, net of fees) secured by four Boeing 737-800 aircraft. These borrowings, which were recorded as a financing transaction in the Company's Consolidated Statement of Cash Flows, and as debt in the accompanying Consolidated Balance Sheet, bear interest at a rate equal to the 3 month LIBOR plus 1.4 percent, payable in quarterly installments through September 29, 2025. During 2020, the Company issued $2.0 billion of unsecured notes due 2027, of which $1.3 billion was issued June 8, 2020 (the “$1.3 billion 2027 Notes”) and $700 million was issued July 31, 2020 (the “$700 million 2027 Notes”). The notes bear interest at 5.125%. Interest is payable semi-annually in arrears on June 15 and December 15, beginning December 15, 2020. The $700 million 2027 Notes were offered as an additional issuance of the Company’s $1.3 billion 2027 Notes issued on June 8, 2020. The $700 million 2027 Notes were issued at a premium and this premium has been included within Capitalized financing items in the Consolidated Statement of Cash Flows. A portion of the proceeds from the $1.3 billion 2027 Notes were used to repay a portion of the outstanding Amended and Restated 364-Day Credit Agreement balance. See below for more information regarding the Amended and Restated 364-Day Credit Agreement. In second quarter 2020, the Company, through special purpose entities, entered into agreements with a financing institution and trusts to borrow $197 million ($190 million, net of fees) secured by six Boeing 737-800 aircraft. These borrowings, which were recorded as a financing transaction in the Company's Consolidated Statement of Cash Flows, and as debt in the accompanying unaudited Condensed Consolidated Balance Sheet, bear interest at a rate equal to the 3 month LIBOR plus 1.4 percent, payable in quarterly installments through June 30, 2028. The special purpose entities were determined to be variable interest entities for which the Company is the primary beneficiary, and therefore were consolidated in the accompanying Consolidated Financial Statements. During 2020, the Company issued $1.55 billion of unsecured notes due 2025, of which $1.25 billion was issued May 4, 2020 (the “$1.25 billion 2025 Notes”) and $300 million was issued July 31, 2020 (the “$300 million 2025 Notes”). The notes bear interest at 5.250%. Interest is payable semi-annually in arrears on May 4 and November 4, beginning November 4, 2020. The $300 million 2025 Notes were offered as an additional issuance of the Company’s $1.25 billion 2025 Notes issued on May 4, 2020. The $300 million 2025 Notes were issued at a premium and this premium has been included within Capitalized financing items in the Consolidated Statement of Cash Flows. The proceeds from the $1.25 billion 2025 Notes were used to repay a portion of the outstanding Amended and Restated 364-Day Credit Agreement balance. During 2020, the Company issued $1.25 billion of unsecured notes due 2023, of which $750 million was issued May 4, 2020 (the “$750 million 2023 Notes”) and $500 million was issued June 8, 2020 (the “$500 million 2023 Notes”). The notes bear interest at 4.750%. Interest is payable semi-annually in arrears on May 4 and November 4, beginning November 4, 2020. The $500 million 2023 Notes were offered as an additional issuance of the Company's $750 million 2023 Notes issued on May 4, 2020. The $500 million 2023 Notes were issued at a premium and this premium has been included within Capitalized financing items in the Consolidated Statement of Cash Flows. The proceeds from the $750 million 2023 Notes and a portion of the proceeds of the $500 million 2023 Notes were used to repay a portion of the outstanding Amended and Restated 364-Day Credit Agreement balance. On May 1, 2020, the Company completed the public offering of $2.3 billion aggregate principal amount of 1.250% Convertible Senior Notes due 2025 (the “Convertible Notes”), which included the full exercise of the underwriters' option to buy an additional $300 million aggregate principal amount of Convertible Notes. The Convertible Notes bear interest at the rate of 1.25% per year and will mature on May 1, 2025. Interest on the notes is payable semi-annually in arrears on May 1 and November 1 of each year, beginning on November 1, 2020. Holders may convert their Convertible Notes at their option at any time prior to the close of business on the business day immediately preceding February 1, 2025, only under the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on June 30, 2020 (and only during such calendar quarter), if the last reported sale price of the common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130 percent of the conversion price on each applicable trading day; (2) during the five business day period after any ten consecutive trading day period in which the trading price per $1,000 principal amount of Convertible Notes for each trading day of the measurement period was less than 98 percent of the product of the last reported sale price of the Company’s common stock and the conversion rate on each such trading day; or (3) upon the occurrence of specified corporate events as defined. On or after February 1, 2025, until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert their notes at any time, regardless of the foregoing circumstances. As of December 31, 2020, conditions had not been met to convert. Upon conversion, the Company will pay or deliver, as the case may be, cash, shares of the Company’s common stock or a combination of cash and shares of common stock, at the Company’s election. The Company intends, however, to settle conversions by paying cash up to the principal amount, with any excess conversion value settled in shares of common stock. The initial conversion rate is 25.9909 shares of common stock per $1,000 principal amount of Convertible Notes (equivalent to an initial conversion price of approximately $38.48 per share of common stock). The conversion rate will be subject to adjustment in some events, but will not be adjusted for any accrued and unpaid interest. In addition, in the event of certain corporate events that occur prior to the maturity date, the Company will increase the conversion rate for a holder who elects to convert its Convertible Notes in connection with such a corporate event in certain circumstances. In the event of a “Fundamental Change,” as defined, the holders may require the Company to purchase for cash all or a portion of their notes at a purchase price equal to 100 percent of the principal amount of the notes, plus accrued and unpaid interest, if any. The Company may not redeem the notes at its option prior to the maturity date. Upon issuance, the Company bifurcated the Convertible Notes for accounting purposes between a liability component and an equity component utilizing applicable guidance. The liability component was determined by estimating the fair value of a hypothetical issuance of an identical offering excluding the conversion feature of the Convertible Notes, which has been estimated at $1.9 billion, and is reflected as a component of Long-term debt in the Consolidated Balance Sheet. The effective interest rate of this liability was 5.2 percent. The equity component was calculated as the difference between the liability component and the face amount of the Convertible Notes, determined to be $403 million, and was classified within Additional paid in capital in the Consolidated Balance Sheet. The Convertible Notes proceeds are also shown within the financing activities section in the Consolidated Statement of Cash Flows. The amount of the equity component in the transaction also represents a discount on the liability portion of the Convertible Notes, and as such is being amortized as a non-cash component of interest expense over the 5-year term of the notes. The costs incurred in the issuance, including underwriters' discount, totaling $62 million, are classified as a cash outflow within the financing activities section in the Consolidated Statement of Cash Flows, and is also being amortized to expense over the term of the notes. Issuance costs attributable to the equity component of $11 million were netted with the equity component in the Consolidated Statement of Stockholders' Equity. The amortization expense for debt discounts and debt issuance costs for 2020 was $48 million and $5 million, respectively. The Company did not have convertible instruments during 2019 or 2018. Because the Company intends to settle conversions by paying cash up to the principal amount of the Convertible Notes, with any excess conversion value settled in shares of common stock, the Convertible Notes are being accounted for using the treasury stock method for the purposes of Net income (loss) per share. Using this method, the denominator will be affected when the average share price of the Company's common stock for a given period is greater than the conversion price of approximately $38.48 per share. The Convertible Notes stipulated that holders of the notes may not elect to convert their Convertible Notes to shares of common stock until after June 30, 2020, and therefore there was no dilutive impact related to the notes prior to July 1, 2020. As consideration for the Payroll Support funding, the Company agreed to issue Warrants to the Treasury to purchase the Company's common stock in connection with each disbursement of Payroll Support to the Company. The Company accounts for the Warrants using the treasury stock method. Using this method, the denominator will be affected when the average share price of the Company's common stock for a given period is greater than the warrant exercise price of $36.47 per share. While the Company is reporting a net loss, all potential shares are considered antidilutive and have no impact on Net income (loss) per share. On March 12, 2020, the Company entered into a new $1.0 billion 364-day term loan credit facility agreement (the “364-Day Credit Agreement”) with a syndicate of lenders identified in the 364-Day Credit Agreement. The 364-Day Credit Agreement was drawn in full on the closing date. On March 30, 2020, the Company amended and restated the 364-Day Credit Agreement (the “Amended and Restated 364-Day Credit Agreement”) with a syndicate of lenders identified in the Amended and Restated 364-Day Credit Agreement to add additional term loan commitments of approximately $2.3 billion, add an uncommitted accordion increase provision to permit additional term loans in an aggregate amount not to exceed approximately $417 million, amend the pricing, amend certain covenants, add certain covenants, and provide for the grant of a security interest in certain aircraft and related assets. The Company drew approximately $2.3 billion under the Amended and Restated 364-Day Credit Agreement on April 1, 2020. On April 24, 2020, the Company drew an additional $350 million under the $417 million accordion feature. The Amended and Restated 364-Day Credit Agreement was originally set to mature in full on March 29, 2021. The outstanding Amended and Restated 364-Day Credit Agreement balance was repaid in full in second quarter 2020, and the agreement has been terminated. Concurrently with entering into the Amended and Restated 364-Day Credit Agreement on March 30, 2020, the Company also amended its existing $1.0 billion revolving credit facility expiring in August 2022 (the “Amended and Restated Revolving Credit Agreement”) to (i) amend the pricing and fees, (ii) amend certain covenants and provisions, (iii) add certain covenants, and (iv) provide for the grant of a security interest in certain aircraft and related assets. In second quarter 2020, the Company repaid in full the $1.0 billion drawn on the Amended and Restated Revolving Credit Agreement. On November 23, 2020, the Company amended the Amended and Restated Revolving Credit Agreement to (i) amend the pricing and fees, (ii) amend certain covenants and provisions, (iii) remove a financial covenant, and (iv) amend an exhibit for conforming changes to the compliance certificate (the "Amendment," and the Amended and Restated Revolving Credit Agreement as amended by the Amendment, the "Amended A&R Credit Agreement"). The amount of the loan commitments, the tenor, and the collateral under the Amended and Restated Revolving Credit Agreement remain unchanged by the Amendment. As of December 31, 2020, there were no amounts outstanding under the Amended A&R Credit Agreement. Generally, amounts outstanding under the Amended A&R Credit Agreement bear interest at interest rates based on either the LIBOR rate (selected by the Company for designated interest periods) or the “alternate base rate” (being the highest of (1) the Wall Street Journal prime rate, (2) one-month adjusted LIBOR (one-month LIBOR plus a statutory reserve rate) plus 1 percent, and (3) the New York Fed Bank Rate, plus 0.5 percent). The underlying LIBOR rate is subject to a floor of 1 percent per annum and the “alternate base rate” is subject to a floor of 1 percent per annum. The Amended A&R Credit Agreement contains customary representations and warranties, covenants, and events of default. The Amended A&R Credit Agreement is secured by a pool of 73 aircraft and related assets, each with a minimum appraised value ratio requirement. Under the Amended A&R Credit Agreement, the Company is required to maintain a minimum level of liquidity of $1.5 billion (defined as the sum of (i) the aggregate amount available to be borrowed under the Amended A&R Credit Agreement plus (ii) the aggregate amount of unrestricted cash and cash equivalents of the Company plus (iii) the aggregate amount of short-term investments of the Company). As of December 31, 2020, the Company was in compliance with this covenant and all other covenants in the Amended A&R Credit Agreement. The Amended A&R Credit Agreement is a series of short-term borrowings; at the end of each borrowing the Company must elect to roll the facility over into the next borrowing or pay down the facility. The Amended A&R Credit Agreement has an accordion feature that would allow the Company, subject to, among other things, the procurement of incremental commitments, to increase the size of the facility to $1.5 billion. During February 2020, the Company issued $500 million senior unsecured notes due 2030. The notes bear interest at 2.625 percent. Interest is payable semi-annually in arrears on February 10 and August 10, beginning in 2020. During November 2017, the Company issued $300 million senior unsecured notes due 2022. The notes bear interest at 2.75 percent. Interest is payable semi-annually in arrears on May 16 and November 16. Also during November 2017, the Company issued $300 million senior unsecured notes due 2027. The notes bear interest at 3.45 percent. Interest is payable semi-annually in arrears on May 16 and November 16. During November 2016, the Company issued $300 million senior unsecured notes due 2026. The notes bear interest at 3.00 percent. Interest is payable semi-annually in arrears on May 15 and November 15. During October 2016, the Company entered into a term loan agreement providing for loans to the Company aggregating up to $215 million, to be secured by mortgages on seven of the Company's 737-800 aircraft. The Company borrowed the full $215 million and secured this loan with the requisite seven aircraft mortgages. The loan matures on October 31, 2026, and is repayable via semi-annual installments of principal that began on April 30, 2018. The loan bears interest at the LIBO Rate (as defined in the term loan agreement) plus 1.10 percent, which equates to a current rate of 1.34 percent, and interest is payable semi-annually in installments. During November 2015, the Company issued $500 million senior unsecured notes due 2020. The notes bore interest at 2.65 percent, payable semi-annually in arrears on May 5 and November 5. Concurrently, the Company entered into a fixed-to-floating interest rate swap to convert the interest on these unsecured notes to a floating rate until their maturity. The notes were redeemed early in full on October 5, 2020, utilizing available cash on hand. On May 6, 2008, the Company entered into a term loan agreement providing for loans to the Company aggregating up to $600 million, to be secured by first-lien mortgages on 21 of the Company’s 737-700 aircraft. On May 9, 2008, the Company borrowed the full $600 million and secured these loans with the requisite 21 aircraft mortgages. The loans matured and were fully repaid on May 9, 2020. The loans bore interest at the LIBO Rate (as defined in the term loan agreement) plus 0.95 percent. Pursuant to the terms of the term loan agreement, the Company entered into an interest rate swap agreement to convert the variable rate on the term loan to a fixed 5.223 percent until maturity. On October 3, 2007, grantor trusts established by the Company issued $500 million Pass Through Certificates consisting of $412 million 6.15 percent Series A certificates and $88 million 6.65 percent Series B certificates. A separate trust was established for each class of certificates. The trusts used the proceeds from the sale of certificates to acquire equipment notes in the same amounts, which were issued by the Company on a full recourse basis. Payments on the equipment notes held in each trust are passed through to the holders of certificates of such trust. The equipment notes were issued for each of 16 Boeing 737-700 aircraft owned by the Company and are secured by a mortgage on each aircraft. Beginning February 1, 2008, principal and interest payments on the equipment notes held for both series of certificates became due semi-annually until the balance of the certificates mature on August 1, 2022. Prior to their issuance, the Company also entered into swap agreements to hedge the variability in interest rates on the Pass Through Certificates. The swap agreements were accounted for as cash flow hedges, and resulted in a payment by the Company of $20 million upon issuance of the Pass Through Certificates. The effective portion of the hedge is being amortized to interest expense concurrent with the amortization of the debt and is reflected in the above table as a reduction in the debt balance. The ineffectiveness of the hedge transaction was immaterial. On February 28, 1997, the Company issued $100 million of senior unsecured 7.375 percent debentures due March 1, 2027. Interest is payable semi-annually on March 1 and September 1. The debentures may be redeemed, at the option of the Company, in whole at any time or in part from time to time, at a redemption price equal to the greater of the principal amount of the debentures plus accrued interest at the date of redemption or the sum of the present values of the remaining scheduled payments of principal and interest thereon, discounted to the date of redemption at the comparable treasury rate plus 20 basis points, plus accrued interest at the date of redemption. The Company is required to provide standby letters of credit to support certain obligations that arise in the ordinary course of business. Although the letters of credit are an off-balance sheet item, the majority of the obligations to which they relate are reflected as liabilities in the Consolidated Balance Sheet. Outstanding letters of credit totaled $138 million at December 31, 2020. The net book value of the assets pledged as collateral for the Company’s secured borrowings, primarily aircraft, was $2.1 billion at December 31, 2020. Other Financings During 2020, the Company entered into sale-leaseback arrangements and issued common stock. See Notes 8 and 9, respectively, for further information. As of December 31, 2020, aggregate annual principal maturities of debt and finance leases (not including amounts associated with interest on finance leases) for the five-year period ending December 31, 2025, and thereafter, were $220 million in 2021, $524 million in 2022, $1.4 billion in 2023, $152 million in 2024, $4.0 billion in 2025, and $4.4 billion thereafter.

LEASES

LEASES	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
LEASES	LEASESThe Company enters into leases for aircraft, property, and other types of equipment in the normal course of business. The accounting for these leases follows the requirements of the New Lease Standard, which the Company adopted as of January 1, 2019. See Note 3 for further information. As of December 31, 2020, the Company held aircraft leases with remaining terms ranging from one month to 13 years. The aircraft leases generally can be renewed for three months to six years at rates based on fair market value at the end of the lease term. Residual value guarantees included in the Company's lease agreements are not material. On July 9, 2012, the Company signed an agreement with Delta Air Lines, Inc. and Boeing Capital Corp. to lease or sublease 88 AirTran Airways, Inc. Boeing 717-200 aircraft ("B717s") to Delta at agreed-upon lease rates. Eight and 20 operating leases expired during 2019 and 2020, respectively. Ten owned B717s were sold in 2019. The proceeds from the sale, which were not material, were netted within Capital expenditures in the Consolidated Statement of Cash Flows. Excluding the 20 aircraft for which operating leases expired during 2020, the following remained: 45 on operating leases and two on finance leases. The sublease terms for the 45 B717s on operating lease and the two B717s on finance lease coincide with the Company's remaining lease terms for these aircraft from the original lessor, which have remaining lease terms ranging from approximately one month to four years. The Company's future sublease income associated with the 45 B717s on operating lease as of December 31, 2020, was as follows: $41 million in 2021, $17 million in 2022, $7 million in 2023, and $1 million in 2024. The two B717s classified by the Company as finance leases are accounted for as direct financing leases, and the remaining 45 subleases are accounted for as operating leases. There are no contingent payments and no significant residual value conditions associated with the transaction. In second quarter 2020, the Company entered into transactions with third parties, involving ten of the Company’s Boeing 737-800 aircraft and ten of the Company's Boeing 737 MAX 8 aircraft that qualified as sale-leaseback arrangements under applicable accounting guidance. The Company sold the ten 737-800 aircraft to a third party for $405 million, then immediately leased the aircraft back for approximately ten years. The Company sold the ten 737 MAX 8 aircraft to a third party for $410 million, then immediately leased the aircraft back for approximately 13 years. As such, the aircraft were de-recognized from Property and equipment at their remaining net book values. All of the leases from the sale-leasebacks are accounted for as operating leases, and thus are now reflected as part of the Company’s Operating lease right-of-use assets and operating lease liabilities in the accompanying Consolidated Balance Sheet. The 737-800 and 737 MAX 8 sale-leaseback transactions resulted in a recognized gain of $153 million and $69 million, respectively, reflected within Other operating expenses, net in the accompanying Consolidated Statement of Comprehensive Income (Loss). At each airport where the Company conducts flight operations, the Company has lease agreements, generally with a governmental unit or authority, for the use of airport terminals, airfields, office space, cargo warehouses, gates, and/or maintenance facilities. These leases are classified as operating lease agreements and have lease terms remaining ranging from one month to 40 years. Certain leases can be renewed from 6 months to ten years. The majority of the airport terminal leases contain certain provisions for periodic adjustments to rates that depend upon airport operating costs or use of the facilities, and are reset at least annually. Due to the nature and variability of the rates, the majority of these leases are not recorded on the Consolidated Balance Sheet. The Company also leases certain technology assets, fuel storage tanks, and various other equipment that qualify as leases under the applicable accounting guidance. The remaining lease terms range from three months to six years. Certain leases can be renewed from six months to five years. Lease-related assets and liabilities recorded on the Consolidated Balance Sheet were as follows: (in millions) Balance Sheet location December 31, 2020 December 31, 2019 Assets Operating Operating lease right-of-use assets (net) $ 1,892 $ 1,349 Finance Property and equipment (net of allowance for depreciation and amortization of $567 and $455) 667 779 Total lease assets $ 2,559 $ 2,128 Liabilities Current Operating Current operating lease liabilities $ 306 $ 353 Finance Current maturities of long-term debt 83 85 Noncurrent Operating Noncurrent operating lease liabilities 1,562 978 Finance Long-term debt less current maturities 459 542 Total lease liabilities $ 2,410 $ 1,958 The components of lease costs, included in the Consolidated Statement of Comprehensive Income (Loss), were as follows: (in millions) Statement of Comprehensive Income (Loss) location Year ended December 31, 2020 Year ended December 31, 2019 Operating lease cost - aircraft (a) Other operating expenses $ 216 $ 182 Operating lease cost - other Landing fees and airport rentals, and Other operating expenses 89 89 Short-term lease cost Other operating expenses 1 4 Variable lease cost Landing fees and airport rentals, and Other operating expenses 1,260 1,377 Finance lease cost: Amortization of lease liabilities Depreciation and amortization 113 116 Interest on lease liabilities Interest expense 22 26 Total net finance lease cost $ 135 $ 142 (a) Net of sublease income of $78 million and $97 million for the years ended December 31, 2020 and 2019. Supplemental cash flow information related to leases, included in the Consolidated Statement of Cash Flows, was as follows: ( in millions ) Year ended December 31, 2020 Year ended December 31, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 398 $ 379 Operating cash flows for finance leases 22 26 Financing cash flows for finance leases 85 85 Right-of-use assets obtained in exchange for lease obligations: Operating leases 915 230 Finance leases — 1 As of December 31, 2020, maturities of lease liabilities were as follows: ( in millions ) Operating leases Finance leases 2021 $ 371 $ 102 2022 253 98 2023 219 94 2024 193 90 2025 156 74 Thereafter 1,156 156 Total lease payments $ 2,348 $ 614 Less imputed interest (480) (72) Total lease obligations 1,868 542 Less current obligations (306) (83) Long-term lease obligations $ 1,562 $ 459 The table below presents additional information related to the Company's leases: Weighted average remaining lease term December 31, 2020 December 31, 2019 Operating leases 10 years 9 years Finance leases 7 years 8 years Weighted average discount rate Operating leases (a) 3.8 % 3.7 % Finance leases 3.8 % 3.8 % (a) Upon adoption of the New Lease Standard, the incremental borrowing rate used for existing leases was established as of January 1, 2019. As of December 31, 2020, the Company had additional operating lease commitments that had not yet commenced of approximately $291 million for nine Boeing 737 MAX 8 aircraft contractually to be delivered in 2021, each with lease terms of nine years.

COMMON STOCK

COMMON STOCK	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
COMMON STOCK	COMMON STOCK The Company has one class of capital stock, its common stock. On May 1, 2020, the Company completed the public offering of 80.5 million shares of $1.00 par value common stock of the Company, which included the full exercise of the underwriters’ option to purchase an additional 10.5 million shares of common stock, at a public offering price of $28.50 per share. As discussed further in Note 2, in connection with funding that the Company has received under the CARES Act, the Company issued Warrants to acquire up to 2.7 million shares of the Company's common stock to the Treasury. Holders of shares of common stock are entitled to receive dividends when and if declared by the Board of Directors and are entitled to one vote per share on all matters submitted to a vote of the Shareholders. Pursuant to the Payroll Support Program under the CARES Act, as supplemented by the Payroll Support Program Extension, the Company is prohibited from paying dividends with respect to its common stock through March 31, 2022. See Note 2 for further information on the CARES Act. At December 31, 2020, the Company had 60 million shares of common stock reserved for issuance pursuant to Employee equity plans (of which 25 million shares had not been granted) through various share-based compensation arrangements. See Note 10 to the Consolidated Financial Statements for information regarding the Company's equity plans.

STOCK PLANS

STOCK PLANS	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
STOCK PLANS	STOCK PLANS Share-based Compensation The Company accounts for share-based compensation utilizing fair value, which is determined on the date of grant for all instruments. The Consolidated Statement of Income (Loss) for the years ended December 31, 2020, 2019, and 2018, reflects share-based compensation expense of $17 million, $55 million, and $46 million, respectively. The total tax impact recognized in earnings from share-based compensation arrangements for the years ended December 31, 2020, 2019, and 2018, was not material. As of December 31, 2020, there was $29 million of total unrecognized compensation cost related to share-based compensation arrangements, which is expected to be recognized over a weighted-average period of 1.8 years. The Company expects substantially all unvested shares associated with time-based restricted stock unit awards to vest. Restricted Stock Units and Stock Grants Under the Company’s Amended and Restated 2007 Equity Incentive Plan ("2007 Equity Plan"), which has been approved by Shareholders, the Company granted restricted stock units ("RSUs") and performance-based restricted stock units ("PBRSUs") to certain Employees during 2020, 2019, and 2018. Outstanding RSUs vest over three years, subject generally to the individual’s continued employment or service. PBRSUs granted are subject to the Company’s performance with respect to a three-year simple average of Return on Invested Capital, after taxes and excluding special items, for the defined performance period and are also subject generally to the individual’s continued employment or service. The number of PBRSUs vesting on the vesting date will be interpolated based on the Company's Return on Invested Capital performance and ranges from zero PBRSUs to 200 percent of granted PBRSUs. Forfeiture rates are estimated at the time of grant based on historical actuals for similar grants, and are trued-up to actuals over the vesting period. The Company recognizes all expense on a straight-line basis over the vesting period, with any changes in expense due to the number of PBRSUs expected to vest being modified on a prospective basis. Aggregated information regarding the Company’s RSUs and PBRSUs is summarized below: All Restricted Stock Units Units (000) Wtd. Average Outstanding December 31, 2017 1,294 $ 45.32 Granted 782 (a) 60.80 Vested (670) 45.11 Surrendered (64) 47.05 Outstanding December 31, 2018 1,342 52.56 Granted 994 (b) 57.49 Vested (744) 42.42 Surrendered (47) 57.72 Outstanding December 31, 2019, Unvested 1,545 57.65 Granted 1,235 (c) 56.89 Vested (715) 54.70 Surrendered (103) 58.04 Outstanding December 31, 2020, Unvested 1,962 57.81 (a) Includes 308 thousand PBRSUs (b) Includes 387 thousand PBRSUs (c) Includes 519 thousand PBRSUs In addition, the Company granted approximately 54 thousand shares of unrestricted stock at a weighted average grant price of $29.60 in 2020, approximately 31 thousand shares at a weighted average grant price of $52.01 in 2019, and approximately 28 thousand shares at a weighted average grant price of $53.01 in 2018, to members of its Board of Directors. A remaining balance of up to 19 million shares of the Company’s common stock may be issued pursuant to grants under the 2007 Equity Plan. Employee Stock Purchase Plan Under the Amended and Restated 1991 Employee Stock Purchase Plan ("ESPP"), which has been approved by Shareholders, the Company is authorized to issue up to a remaining balance of 6 million shares of the Company’s common stock to Employees of the Company. These shares may be issued at a price equal to 90 percent of the market value at the end of each monthly purchase period. Common stock purchases are paid for through periodic payroll deductions. The following table provides information about the Company’s ESPP activity during 2020, 2019, and 2018: Employee Stock Purchase Plan (a) Total number Weighted-average of shares Average fair value of each purchased price paid purchase right Year ended (in thousands) per share under the ESPP December 31, 2018 661 $ 50.73 $ 5.64 December 31, 2019 821 $ 47.60 $ 5.29 December 31, 2020 1,386 $ 34.39 $ 3.82 (a) The weighted-average fair value of each purchase right under the ESPP granted is equal to a ten percent discount from the market value of the Common Stock at the end of each monthly purchase period. Taxes Grants of RSUs result in the creation of a deferred tax asset, which is a temporary difference, until the time the RSU vests. All excess tax benefits and tax deficiencies are recorded through the income statement. Due to the treatment of RSUs for tax purposes, the Company’s effective tax rate from year to year is subject to variability.

FINANCIAL DERIVATIVE INSTRUMENT

FINANCIAL DERIVATIVE INSTRUMENTS	12 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
FINANCIAL DERIVATIVE INSTRUMENTS	(550)(b) (125) to (150) or >(550)(c) (c) N/A If credit rating is investment Cash is provided to CP >(100) >(50) (75) to (150) or >(550)(d) (125) to (150) or >(550)(d) >(40) >(65)(d) Cash is received from CP >0(d) >150(d) >250(d) >(125)(d) >100(d) >70(d) Cash can be pledged to (200) to (600)(e) N/A (150) to (550)(b) (150) to (550)(b) N/A N/A If credit rating is non-investment Cash is provided to CP (0) to (200) or >(600) (f) (0) to (150) or >(550) (0) to (150) or >(550) (f) (f) Cash is received from CP (f) (f) (f) (f) (f) (f) Cash can be pledged to (200) to (600) N/A (150) to (550) (150) to (550) N/A N/A (a) Individual counterparties with fair value of fuel derivatives <$10 million. (b) The Company has the option of providing cash or letters of credit as collateral. (c) The Company has the option to substitute letters of credit for 100 percent of cash collateral requirement. (d) Thresholds may vary based on changes in credit ratings within investment grade. (e) The Company has the option of providing cash as collateral. " id="sjs-B4" xml:space="preserve">FINANCIAL DERIVATIVE INSTRUMENTS Fuel Contracts Airline operators are inherently dependent upon energy to operate and, therefore, are impacted by changes in jet fuel prices. Furthermore, jet fuel and oil typically represents one of the largest operating expenses for airlines. The Company endeavors to acquire jet fuel at the lowest possible cost and to reduce volatility in operating expenses through its fuel hedging program. Although the Company may periodically enter into jet fuel derivatives for short-term timeframes, because jet fuel is not widely traded on an organized futures exchange, there are limited opportunities to hedge directly in jet fuel for time horizons longer than approximately 24 months into the future. However, the Company has found that financial derivative instruments in other commodities, such as West Texas Intermediate ("WTI") crude oil, Brent crude oil, and refined products, such as heating oil and unleaded gasoline, can be useful in decreasing its exposure to jet fuel price volatility. The Company does not purchase or hold any financial derivative instruments for trading or speculative purposes. The Company has used financial derivative instruments for both short-term and long-term timeframes, and primarily uses a mixture of purchased call options, collar structures (which include both a purchased call option and a sold put option), call spreads (which include a purchased call option and a sold call option), put spreads (which include a purchased put option and a sold put option), and fixed price swap agreements in its portfolio. Although the use of collar structures and swap agreements can reduce the overall cost of hedging, these instruments carry more risk than purchased call options in that the Company could end up in a liability position when the collar structure or swap agreement settles. With the use of purchased call options and call spreads, the Company cannot be in a liability position at settlement, but does not have coverage once market prices fall below the strike price of the purchased call option. For the purpose of evaluating its net cash spend for jet fuel and for forecasting its future estimated jet fuel expense, the Company evaluates its hedge volumes strictly from an "economic" standpoint and thus does not consider whether the hedges have qualified or will qualify for hedge accounting. The Company defines its "economic" hedge as the net volume of fuel derivative contracts held, including the impact of positions that have been offset through sold positions, regardless of whether those contracts qualify for hedge accounting. The level at which the Company is economically hedged for a particular period is also dependent on current market prices for that period, as well as the types of derivative instruments held and the strike prices of those instruments. For example, the Company may enter into "out-of-the-money" option contracts (including catastrophic protection), which may not generate intrinsic gains at settlement if market prices do not rise above the option strike price. Therefore, even though the Company may have an economic hedge in place for a particular period, that hedge may not produce any hedging gains at settlement and may even produce hedging losses depending on market prices, the types of instruments held, and the strike prices of those instruments. For 2020, the Company had fuel derivative instruments in place for up to 77 percent of its fuel consumption. As of December 31, 2020, the Company also had fuel derivative instruments in place to provide coverage at varying price levels. The following table provides information about the Company’s volume of fuel hedging on an economic basis: Maximum fuel hedged as of December 31, 2020 Derivative underlying commodity type as of Period (by year) (gallons in millions) (a) December 31, 2020 2021 1,283 WTI crude oil and Brent crude oil 2022 1,220 WTI crude oil and Brent crude oil 2023 643 WTI crude oil and Brent crude oil Beyond 2023 101 WTI crude oil (a) Due to the types of derivatives utilized by the Company and different price levels of those contracts, these volumes represent the maximum economic hedge in place and may vary significantly as market prices and the Company's flight schedule fluctuate. Upon proper qualification, the Company accounts for its fuel derivative instruments as cash flow hedges. All periodic changes in fair value of the derivatives designated as hedges are recorded in AOCI until the underlying jet fuel is consumed. See Note 13. The Company's results are subject to the possibility that the derivatives will no longer qualify for hedge accounting, in which case any change in the fair value of derivative instruments since the last reporting period would be recorded in Other (gains) losses, net, in the Consolidated Statement of Income (Loss) in the period of the change; however, any amounts previously recorded to AOCI would remain there until such time as the original forecasted transaction occurs, at which time these amounts would be reclassified to Fuel and oil expense. Factors that have and may continue to lead to the loss of hedge accounting include: significant fluctuation in energy prices, significant weather events affecting refinery capacity and the production of refined products, and the volatility of the different types of products the Company uses in hedging. Increased volatility in these commodity markets for an extended period of time, especially if such volatility were to worsen, could cause the Company to lose hedge accounting altogether for the commodities used in its fuel hedging program, which would create further volatility in the Company’s GAAP financial results. However, even though derivatives may not qualify for hedge accounting, the Company continues to hold the instruments as management believes derivative instruments continue to afford the Company the opportunity to stabilize jet fuel costs. When the Company has sold derivative positions in order to effectively "close" or offset a derivative already held as part of its fuel derivative instrument portfolio, any subsequent changes in fair value of those positions are marked to market through earnings. Likewise, any changes in fair value of those positions that were offset by entering into the sold positions and were de-designated as hedges are concurrently marked to market through earnings. However, any changes in value related to hedges that were deferred as part of AOCI while designated as a hedge would remain until the originally forecasted transaction occurs. In a situation where it becomes probable that a fuel hedged forecasted transaction will not occur, any gains and/or losses that have been recorded to AOCI would be required to be immediately reclassified into earnings. During 2020, as a result of the drastic drop in demand for air travel due to the COVID-19 pandemic, the Company's forecast for 2020 and 2021 fuel purchases and consumption was significantly reduced, causing the Company to be in an estimated "over-hedged" position for second, third, and fourth quarter 2020, and full year 2021. Therefore, the Company de-designated a portion of its fuel hedges related to these periods, and has reclassified approximately $39 million in losses from AOCI into Other (gains) losses, net, during 2020. The Company did not have any such situations occur during 2019 or 2018. Accounting pronouncements pertaining to derivative instruments and hedging are complex with stringent requirements, including the documentation of a Company hedging strategy, statistical analysis to qualify a commodity for hedge accounting both on a historical and a prospective basis, and strict contemporaneous documentation that is required at the time each hedge is designated by the Company. This statistical analysis involves utilizing regression analyses that compare changes in the price of jet fuel to changes in the prices of the commodities used for hedging purposes. All cash flows associated with purchasing and selling fuel derivatives are classified as Other operating cash flows in the Consolidated Statement of Cash Flows. The following table presents the location of all assets and liabilities associated with the Company’s derivative instruments within the Consolidated Balance Sheet: Asset derivatives Liability derivatives Balance Sheet Fair value at Fair value at Fair value at Fair value at (in millions) location 12/31/2020 12/31/2019 12/31/2020 12/31/2019 Derivatives designated as hedges (a) Fuel derivative contracts (gross) Prepaid expenses and other current assets $ 9 $ 48 $ — $ — Fuel derivative contracts (gross) Other assets 121 62 — — Interest rate derivative contracts Other assets — 2 — — Interest rate derivative contracts Accrued liabilities — — — 5 Interest rate derivative contracts Other noncurrent liabilities — — 6 1 Total derivatives designated as hedges $ 130 $ 112 $ 6 $ 6 Derivatives not designated as hedges (a) Fuel derivative contracts (gross) Prepaid expenses and other current assets $ 4 $ — $ — $ — Total derivatives $ 134 $ 112 $ 6 $ 6 (a) Represents the position of each trade before consideration of offsetting positions with each counterparty and does not include the impact of cash collateral deposits provided to or received from counterparties. See discussion of credit risk and collateral following in this Note. In addition, the Company had the following amounts associated with fuel derivative instruments and hedging activities in its Consolidated Balance Sheet: Balance Sheet December 31, December 31, (in millions) location 2020 2019 Cash collateral deposits held from counterparties for fuel contracts - current Offset against Prepaid expenses and other current assets $ 3 $ 10 Cash collateral deposits held from counterparties for fuel contracts - noncurrent Offset against Other assets 31 15 All of the Company's fuel derivative instruments and interest rate swaps are subject to agreements that follow the netting guidance in the applicable accounting standards for derivatives and hedging. The types of derivative instruments the Company has determined are subject to netting requirements in the accompanying Consolidated Balance Sheet are those in which the Company pays or receives cash for transactions with the same counterparty and in the same currency via one net payment or receipt. For cash collateral held by the Company or provided to counterparties, the Company nets such amounts against the fair value of the Company's derivative portfolio by each counterparty. The Company has elected to utilize netting for both its fuel derivative instruments and interest rate swap agreements and also classifies such amounts as either current or noncurrent, based on the net fair value position with each of the Company's counterparties in the Consolidated Balance Sheet. If its fuel derivative instruments are in a net asset position with a counterparty, cash collateral amounts held are first netted against current outstanding derivative asset amounts associated with that counterparty until that balance is zero, and then any remainder is applied against the fair value of noncurrent outstanding derivative instruments. No cash collateral deposits were provided by or held by the Company based on its outstanding interest rate swap agreements. The Company has the following recognized financial assets and financial liabilities resulting from those transactions that meet the scope of the disclosure requirements as necessitated by applicable accounting guidance for balance sheet offsetting: Offsetting of derivative assets (in millions) (i) (ii) (iii) = (i) + (ii) (i) (ii) (iii) = (i) + (ii) December 31, 2020 December 31, 2019 Description Balance Sheet location Gross amounts of recognized assets Gross amounts offset in the Balance Sheet Net amounts of assets presented in the Balance Sheet Gross amounts of recognized assets Gross amounts offset in the Balance Sheet Net amounts of assets presented in the Balance Sheet Fuel derivative contracts Prepaid expenses and other current assets $ 13 $ (3) $ 10 $ 48 $ (10) $ 38 Fuel derivative contracts Other assets $ 121 $ (31) $ 90 (a) $ 62 $ (15) $ 47 (a) Interest rate derivative contracts Other assets $ — $ — $ — (a) $ 2 $ — $ 2 (a) (a) The net amounts of derivative assets and liabilities are reconciled to the individual line item amounts presented in the Consolidated Balance Sheet in Note 16. Offsetting of derivative liabilities (in millions) (i) (ii) (iii) = (i) + (ii) (i) (ii) (iii) = (i) + (ii) December 31, 2020 December 31, 2019 Description Balance Sheet location Gross amounts of recognized liabilities Gross amounts offset in the Balance Sheet Net amounts of liabilities presented in the Balance Sheet Gross amounts of recognized liabilities Gross amounts offset in the Balance Sheet Net amounts of liabilities presented in the Balance Sheet Fuel derivative contracts Prepaid expenses and other current assets $ 3 $ (3) $ — $ 10 $ (10) $ — Fuel derivative contracts Other assets $ 31 $ (31) $ — (a) $ 15 $ (15) $ — (a) Interest rate derivative contracts Accrued liabilities $ — $ — $ — $ 5 $ — $ 5 Interest rate derivative contracts Other noncurrent liabilities $ 6 $ — $ 6 $ 1 $ — $ 1 (a) The net amounts of derivative assets and liabilities are reconciled to the individual line item amounts presented in the Consolidated Balance Sheet in Note 16. The following tables present the impact of derivative instruments and their location within the Consolidated Statement of Income (Loss) for the year ended December 31, 2020 and 2019: Location and amount recognized in income on cash flow and fair value hedging relationships Year ended December 31, 2020 Year ended December 31, 2019 (in millions) Fuel and oil Other (gains)/losses, net Interest expense Fuel and oil Interest expense Total $ 70 $ 39 $ 6 $ 48 $ 29 Loss on cash flow hedging relationships Commodity contracts: Amount of loss reclassified from AOCI into income 70 39 — 48 — Interest contracts: Amount of loss reclassified from AOCI into income — — 1 — 5 Impact of fair value hedging relationships: Interest contracts: Hedged items — — 11 — 22 Derivatives designated as hedging instruments — — (6) — 2 Derivatives designated and qualified in cash flow hedging relationships Loss recognized in AOCI on derivatives, net of tax Year ended December 31, (in millions) 2020 2019 Fuel derivative contracts $ 80 $ 90 Interest rate derivatives 26 29 Total $ 106 $ 119 Derivatives not designated as hedges Loss recognized in income on derivatives Year ended December 31, Location of loss recognized in income on derivatives (in millions) 2020 2019 Fuel derivative contracts $ 1 $ — Other (gains) losses, net Interest rate derivatives 28 — Other (gains) losses, net Total $ 29 $ — The Company also recorded expense associated with premiums paid for fuel derivative contracts that settled/expired during 2020, 2019, and 2018. Gains and/or losses associated with fuel derivatives that qualify for hedge accounting are ultimately recorded to Fuel and oil expense. Gains and/or losses associated with fuel derivatives that do not qualify for hedge accounting are recorded to Other (gains) and losses, net. The following table presents the impact of premiums paid for fuel derivative contracts and their location within the Consolidated Statement of Income (Loss) during the period the contract settles: Premium expense recognized in income on derivatives Year ended December 31, Location of premium expense recognized in income on derivatives (in millions) 2020 2019 2018 Fuel derivative contracts designated as hedges $ 64 $ 95 $ 135 Fuel and oil Fuel derivative contracts not designated as hedges $ 34 $ — $ — Other (gains) losses, net The fair values of the derivative instruments, depending on the type of instrument, were determined by the use of present value methods or option value models with assumptions about commodity prices based on those observed in underlying markets or provided by third parties. Included in the Company’s cumulative net unrealized losses from fuel hedges as of December 31, 2020, recorded in AOCI, were approximately $54 million in unrealized losses, net of taxes, which are expected to be realized in earnings during the twelve months subsequent to December 31, 2020. Interest Rate Swaps The Company is party to certain interest rate swap agreements that are accounted for as cash flow hedges, and has in the past held interest rate swap agreements that have qualified as fair value hedges, as defined in the applicable accounting guidance for derivative instruments and hedging. Several of the Company's interest rate swap agreements have historically qualified for the "shortcut" method of accounting for hedges, which dictated that the hedges were assumed to be perfectly effective, and, thus, there was no ineffectiveness to be recorded in earnings. For the Company’s interest rate swap agreements that do not qualify for the "shortcut" or "critical terms match" methods of accounting, ineffectiveness is assessed at each reporting period. If hedge accounting is achieved, all periodic changes in fair value of the interest rate swaps are recorded in AOCI. The ineffectiveness associated with all of the Company’s interest rate swap agreements for all periods presented was not material. During first quarter 2019, the Company entered into 12 separate forward-starting interest rate swap agreements related to a series of 12 Boeing 737 MAX 8 aircraft leases with deliveries originally scheduled between July 2019 and February 2020. These lease contracts exposed the Company to interest rate risk as the rental payments were subject to adjustment and would become fixed based on the 9-year swap rate at the time of delivery. The primary objective of these interest rate derivatives, which qualified as cash flow hedges, was to hedge the forecasted monthly rental payments. These swap agreements provided for a single payment at maturity based upon the change in the 9-year swap rate between the execution date and the termination date. All 12 swap agreements were terminated during third quarter 2019, resulting in $32 million being "frozen" in AOCI. Three of these leased aircraft were received in December 2020 and the remainder are expected to be received during 2021. The earnings impact of the interest rate swaps associated with the aircraft received in 2020 was not material. During third quarter 2019, the Company entered into 12 separate forward-starting interest rate swap agreements, related to a series of 12 Boeing 737 MAX 8 aircraft leases. The third quarter 2019 swaps contain similar terms as the third quarter 2019 terminated swaps discussed above, except that the related 737 MAX 8 deliveries were scheduled to occur between June 2020 and September 2020. During the year ended December 31, 2020, all 12 of the aircraft leases became no longer probable to be received within the scheduled delivery range. Therefore, the 12 associated swap agreements were de-designated and $31 million was "frozen" in AOCI. Three of these aircraft leases were received in December 2020 and the remainder are expected to be received during 2021. The earnings impact of the interest rate swaps associated with the aircraft received in 2020 was not material. The mark-to-market changes for these swap agreements were recorded in earnings, resulting in a $28 million unrealized loss to Other (gains) and losses, net, in the Consolidated Statement of Comprehensive Income (Loss) for the year ended December 31, 2020. In addition, the 12 swap agreements were terminated resulting in $59 million paid to the counterparty during 2020. The fair values of the interest rate swap agreements, which are adjusted regularly, have been aggregated by counterparty for classification in the Consolidated Balance Sheet. Agreements totaling a liability of $6 million are cash flow hedges and are classified as components of Other noncurrent liabilities. The corresponding offsetting adjustment related to the liability associated with the Company’s cash flow hedges is to AOCI. See Note 13. Credit Risk and Collateral Credit exposure related to fuel derivative instruments is represented by the fair value of contracts that are an asset to the Company at the reporting date. At such times, these outstanding instruments expose the Company to credit loss in the event of nonperformance by the counterparties to the agreements. However, the Company has not experienced any significant credit loss as a result of counterparty nonperformance in the past. To manage credit risk, the Company selects and periodically reviews counterparties based on credit ratings, limits its exposure with respect to each counterparty, and monitors the market position of the fuel hedging program and its relative market position with each counterparty. At December 31, 2020, the Company had agreements with all of its active counterparties containing early termination rights and/or bilateral collateral provisions whereby security is required if market risk exposure exceeds a specified threshold amount based on the counterparty's credit rating. The Company also had agreements with counterparties in which cash deposits and letters of credit were required to be posted as collateral whenever the net fair value of derivatives associated with those counterparties exceeds specific thresholds. In certain cases, the Company has the ability to substitute among these different forms of collateral in its discretion. The following table provides the fair values of fuel derivatives, amounts posted as collateral, and applicable collateral posting threshold amounts as of December 31, 2020, at which such postings are triggered: Counterparty (CP) (in millions) A B C D E F Other (a) Total Fair value of fuel derivatives $ 33 $ 15 $ 33 $ 14 $ 17 $ 11 $ 11 $ 134 Cash collateral held from CP 34 — — — — — — 34 Letters of credit (LC) — — — — — — — — Option to substitute LC for cash N/A N/A (75) to (150) or >(550)(b) (125) to (150) or >(550)(c) (c) N/A If credit rating is investment Cash is provided to CP >(100) >(50) (75) to (150) or >(550)(d) (125) to (150) or >(550)(d) >(40) >(65)(d) Cash is received from CP >0(d) >150(d) >250(d) >(125)(d) >100(d) >70(d) Cash can be pledged to (200) to (600)(e) N/A (150) to (550)(b) (150) to (550)(b) N/A N/A If credit rating is non-investment Cash is provided to CP (0) to (200) or >(600) (f) (0) to (150) or >(550) (0) to (150) or >(550) (f) (f) Cash is received from CP (f) (f) (f) (f) (f) (f) Cash can be pledged to (200) to (600) N/A (150) to (550) (150) to (550) N/A N/A (a) Individual counterparties with fair value of fuel derivatives <$10 million. (b) The Company has the option of providing cash or letters of credit as collateral. (c) The Company has the option to substitute letters of credit for 100 percent of cash collateral requirement. (d) Thresholds may vary based on changes in credit ratings within investment grade. (e) The Company has the option of providing cash as collateral.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS Accounting standards pertaining to fair value measurements establish a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value. These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions. As of December 31, 2020, the Company held certain items that are required to be measured at fair value on a recurring basis. These included cash equivalents, short-term investments (primarily treasury bills and certificates of deposit), interest rate derivative contracts, fuel derivative contracts, and available-for-sale securities. The majority of the Company’s short-term investments consist of instruments classified as Level 1. However, the Company has certificates of deposit, commercial paper, and time deposits that are classified as Level 2, due to the fact that the fair value for these instruments is determined utilizing observable inputs in non-active markets. Other available-for-sale securities primarily consist of investments associated with the Company’s excess benefit plan. The Company’s fuel and interest rate derivative instruments consist of over-the-counter contracts, which are not traded on a public exchange. Fuel derivative instruments currently consist solely of option contracts, whereas interest rate derivatives consist solely of swap agreements. See Note 11 for further information on the Company’s derivative instruments and hedging activities. The fair values of swap contracts are determined based on inputs that are readily available in public markets or can be derived from information available in publicly quoted markets. Therefore, the Company has categorized these swap contracts as Level 2. The Company’s Treasury Department, which reports to the Chief Financial Officer, determines the value of option contracts utilizing an option pricing model based on inputs that are either readily available in public markets, can be derived from information available in publicly quoted markets, or are provided by financial institutions that trade these contracts. The option pricing model used by the Company is an industry standard model for valuing options and is the same model used by the broker/dealer community (i.e., the Company’s counterparties). The inputs to this option pricing model are the option strike price, underlying price, risk free rate of interest, time to expiration, and volatility. Because certain inputs used to determine the fair value of option contracts are unobservable (principally implied volatility), the Company has categorized these option contracts as Level 3. Volatility information is obtained from external sources, but is analyzed by the Company for reasonableness and compared to similar information received from other external sources. The fair value of option contracts considers both the intrinsic value and any remaining time value associated with those derivatives that have not yet settled. The Company also considers counterparty credit risk and its own credit risk in its determination of all estimated fair values. To validate the reasonableness of the Company’s option pricing model, on a monthly basis, the Company compares its option valuations to third party valuations. If any significant differences were to be noted, they would be researched in order to determine the reason. However, historically, no significant differences have been noted. The Company has consistently applied these valuation techniques in all periods presented and believes it has obtained the most accurate information available for the types of derivative contracts it holds. Included in Other available-for-sale securities are the Company's investments associated with its deferred compensation plans, which consist of mutual funds that are publicly traded and for which market prices are readily available. These plans are non-qualified deferred compensation plans designed to hold contributions in excess of limits established by the Internal Revenue Code of 1986, as amended. The distribution timing and payment amounts under these plans are made based on the participant's distribution election and plan balance. Assets related to the funded portions of the deferred compensation plans are held in a rabbi trust, and the Company remains liable to these participants for the unfunded portion of the plans. The Company records changes in the fair value of the assets in the Company's earnings. The following tables present the Company’s assets and liabilities that are measured at fair value on a recurring basis at December 31, 2020, and December 31, 2019: Fair value measurements at reporting date using: Quoted prices in active markets for identical assets Significant other observable inputs Significant unobservable inputs Description December 31, 2020 (Level 1) (Level 2) (Level 3) Assets (in millions) Cash equivalents: Cash equivalents (a) $ 10,663 $ 10,663 $ — $ — Commercial paper 90 — 90 — Certificates of deposit 10 — 10 — Time deposits 300 — 300 — Short-term investments: Treasury bills 1,800 1,800 — — Certificates of deposit 46 — 46 — Time deposits 425 — 425 — Fuel derivatives: Option contracts (b) 134 — — 134 Other available-for-sale securities 259 259 — — Total assets $ 13,727 $ 12,722 $ 871 $ 134 Liabilities Interest rate derivatives (see Note 11) $ (6) $ — $ (6) $ — (a) Cash equivalents are primarily composed of money market investments. (b) In the Consolidated Balance Sheet amounts are presented as an asset. See Note 11. Fair value measurements at reporting date using: Quoted prices in active markets for identical assets Significant other observable inputs Significant unobservable inputs Description December 31, 2019 (Level 1) (Level 2) (Level 3) Assets (in millions) Cash equivalents: Cash equivalents (a) $ 1,999 $ 1,999 $ — $ — Commercial paper 535 — 535 — Certificates of deposit 14 — 14 — Short-term investments: Treasury bills 1,196 1,196 — — Certificates of deposit 268 — 268 — Time deposits 60 — 60 — Interest rate derivatives (see Note 11) 2 — 2 — Fuel derivatives: Option contracts (b) 110 — — 110 Other available-for-sale securities 197 197 — — Total assets $ 4,381 $ 3,392 $ 879 $ 110 Liabilities Interest rate derivatives (see Note 11) $ (6) $ — $ (6) $ — (a) Cash equivalents are primarily composed of money market investments. (b) In the Consolidated Balance Sheet amounts are presented as an asset. See Note 11. The Company did not have any material assets or liabilities measured at fair value on a nonrecurring basis as of December 31, 2020 or 2019. The following tables present the Company’s activity for items measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for 2020 and 2019: Fair value measurements using significant unobservable inputs (Level 3) (in millions) Fuel derivatives Balance at December 31, 2019 $ 110 Total (realized or unrealized) losses for the period Included in earnings (40) (a) Included in other comprehensive loss (65) Purchases 129 (b) Balance at December 31, 2020 $ 134 The amount of total losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held at December 31, 2020 $ (15) (a) The amount of total losses for the period included in other comprehensive loss attributable to the change in unrealized gains or losses relating to assets still held at December 31, 2020 $ (41) (a) Included in Other (gains) losses, net, within the Consolidated Statement of Comprehensive Income (Loss). (b) The purchase of fuel derivatives is recorded gross based on the structure of the derivative instrument and whether a contract with multiple derivatives was purchased as a single instrument or separate instruments. Fair value measurements using significant unobservable inputs (Level 3) (in millions) Fuel derivatives Balance at December 31, 2018 $ 138 Total losses (realized or unrealized) included in other comprehensive income (loss) (112) Purchases 133 (a) Sales (2) (a) Settlements (47) Balance at December 31, 2019 $ 110 (a) The purchase and sale of fuel derivatives are recorded gross based on the structure of the derivative instrument and whether a contract with multiple derivatives was purchased as a single instrument or separate instruments. The significant unobservable input used in the fair value measurement of the Company’s derivative option contracts is implied volatility. Holding other inputs constant, an increase (decrease) in implied volatility would have resulted in a higher (lower) fair value measurement, respectively, for the Company’s derivative option contracts. The following table presents a range and weighted average of the unobservable inputs utilized in the fair value measurements of the Company’s fuel derivatives classified as Level 3 at December 31, 2020: Quantitative information about Level 3 fair value measurements Valuation technique Unobservable input Period (by year) Range Weighted Average (a) Fuel derivatives Option model Implied volatility 2021 29-43% 33 % 2022 25-32% 28 % 2023 23-26% 25 % Beyond 2023 25-26% 25 % (a) Implied volatility weighted by the notional amount (barrels of fuel) that will settle in respective period. The carrying amounts and estimated fair values of the Company’s short-term and long-term debt (including current maturities), as well as the applicable fair value hierarchy tier, at December 31, 2020, are presented in the table below. The fair values of the Company’s publicly held long-term debt are determined based on inputs that are readily available in public markets or can be derived from information available in publicly quoted markets; therefore, the Company has categorized these agreements as Level 2. Debt under four of the Company’s debt agreements is not publicly held. The Company has determined the estimated fair value of this debt to be Level 3, as certain inputs used to determine the fair value of these agreements are unobservable. The Company utilizes indicative pricing from counterparties and a discounted cash flow method to estimate the fair value of the Level 3 items. (in millions) Carrying value Estimated fair value Fair value level hierarchy 2.75% Notes due 2022 $ 300 $ 311 Level 2 Pass Through Certificates due 2022 - 6.24% 137 140 Level 2 4.75% Notes due 2023 1,250 1,362 Level 2 1.25% Convertible Notes due 2025 1,945 3,359 Level 2 5.25% Notes due 2025 1,550 1,799 Level 2 Term Loan Agreement payable through 2025 - 1.65% 119 119 Level 3 3.00% Notes due 2026 300 324 Level 2 Term Loan Agreement payable through 2026 - 1.34% 159 155 Level 3 3.45% Notes due 2027 300 329 Level 2 5.125% Notes due 2027 2,000 2,383 Level 2 7.375% Debentures due 2027 119 145 Level 2 Term Loan Agreement payable through 2028 - 1.65% 184 183 Level 3 2.625% Notes due 2030 500 515 Level 2 1.000% Payroll Support Program Loan due 2030 976 953 Level 3

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) Comprehensive income (loss) includes changes in the fair value of certain financial derivative instruments that qualify for hedge accounting, unrealized gains and losses on certain investments, and actuarial gains/losses arising from the Company’s postretirement benefit obligation. A rollforward of the amounts included in AOCI, net of taxes, is shown below for 2020 and 2019: (in millions) Fuel derivatives Interest rate derivatives Defined benefit plan items Other Deferred tax impact Accumulated other Balance at December 31, 2018 $ (56) $ — $ 58 $ 25 $ (7) $ 20 Changes in fair value (117) (38) (38) 34 37 (122) Reclassification to earnings 48 5 — — (12) 41 Balance at December 31, 2019 $ (125) $ (33) $ 20 $ 59 $ 18 $ (61) Changes in fair value (103) (34) (63) 32 39 (129) Reclassification to earnings 109 1 — — (25) 85 Balance at December 31, 2020 $ (119) $ (66) $ (43) $ 91 $ 32 $ (105) The following table illustrates the significant amounts reclassified out of each component of AOCI for the year ended December 31, 2020: Year ended December 31, 2020 (in millions) Amounts reclassified from AOCI Affected line item in the Consolidated Statement of Comprehensive Income (Loss) AOCI components Unrealized loss on fuel derivative instruments $ 70 Fuel and oil expense 39 Other (gains) losses, net 25 Less: Tax expense $ 84 Net of tax Unrealized loss on interest rate derivative instruments $ 1 Interest expense — Less: Tax expense $ 1 Net of tax Total reclassifications for the period $ 85 Net of tax

EMPLOYEE RETIREMENT PLANS

EMPLOYEE RETIREMENT PLANS	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
EMPLOYEE RETIREMENT PLANS	EMPLOYEE RETIREMENT PLANS Defined Contribution Plans Southwest has defined contribution plans covering substantially all of its Employees. Contributions under all defined contribution plans are primarily based on Employee compensation and performance of the Company. The Company sponsors Employee savings plans under section 401(k) of the Internal Revenue Code of 1986, as amended. The Southwest Airlines Co. 401(k) Plan includes Company matching contributions and the Southwest Airlines Pilots Retirement Saving Plan has non-elective Company contributions. In addition, the Southwest Airlines Co. ProfitSharing Plan (ProfitSharing Plan) is a defined contribution plan to which the Company may contribute a percentage of its eligible pre-tax profits, as defined, on an annual basis. No Employee contributions to the ProfitSharing Plan are allowed. Amounts associated with the Company's defined contribution plans expensed in 2020, 2019, and 2018, reflected as a component of Salaries, wages, and benefits, were $561 million, $1.2 billion, and $1.0 billion, respectively. Postretirement Benefit Plans The Company provides postretirement benefits to qualified retirees in the form of medical and dental coverage. Employees must meet minimum levels of service and age requirements as set forth by the Company, or as specified in collective-bargaining agreements with specific workgroups. Employees meeting these requirements, as defined, may use accrued unused sick time to pay for medical and dental premiums from the age of retirement until age 65. The following table shows the change in the accumulated postretirement benefit obligation ("APBO") for the years ended December 31, 2020 and 2019: (in millions) 2020 2019 APBO at beginning of period $ 288 $ 232 Service cost 22 17 Interest cost 10 10 Benefits paid (10) (9) Actuarial loss 63 38 Curtailment 53 — Special termination benefits 2 — APBO at end of period $ 428 $ 288 During 2020, the Company recorded a $63 million actuarial loss as an increase to the APBO with an offset to AOCI. This actuarial loss is reflected above and resulted from changes in certain key assumptions used to determine the Company’s year-end obligation. The assumption change that resulted in the largest portion of the actuarial loss was a reduction in the discount rate used, which caused the funded position to deteriorate. During 2020, the Company also recognized a Curtailment charge and Special termination benefit charge as a result of elections to participate in the plan by eligible Employees upon separating from the Company via Voluntary Separation Plan 2020. See Note 2 for further information. All plans are unfunded, and benefits are paid as they become due. Estimated future benefit payments expected to be paid are $24 million in 2021, $25 million in 2022, $24 million in 2023, $24 million in 2024, $26 million in 2025, and $146 million for the next five years thereafter. The following table reconciles the funded status of the plans to the accrued postretirement benefit cost recognized in Other non-current liabilities on the Company’s Consolidated Balance Sheet at December 31, 2020 and 2019. (in millions) 2020 2019 Funded status $ (428) $ (288) Unrecognized net actuarial (gain) loss 40 (24) Unrecognized prior service cost 3 4 Accumulated other comprehensive income (loss) (43) 20 Consolidated Balance Sheet liability $ (428) $ (288) The consolidated periodic postretirement benefit cost for the years ended December 31, 2020, 2019, and 2018, included the following: (in millions) 2020 2019 2018 Service cost $ 22 $ 17 $ 18 Interest cost 10 10 9 Amortization of prior service cost 1 1 3 Amortization of net gain — (2) — Curtailment 53 — — Special termination benefits 2 — — Net periodic postretirement benefit cost $ 88 $ 26 $ 30 Service cost and Special termination benefits are recognized within Salaries, wages, and benefits expense, and all other costs are recognized in Other (gains) losses, net in the Consolidated Statement of Income (Loss). Unrecognized prior service cost is expensed using a straight-line amortization of the cost over the average future service of Employees expected to receive benefits under the plans. Actuarial gains are amortized utilizing the minimum amortization method. The following actuarial assumptions were used to account for the Company’s postretirement benefit plans at December 31, 2020, 2019, and 2018: 2020 2019 2018 Weighted-average discount rate 2.45 % 3.30 % 4.35 % Assumed healthcare cost trend rate (a) 6.75 % 7.13 % 7.13 % (a) The assumed healthcare cost trend rate is expected to be 6.50% for 2021, then decline gradually to 4.75% by 2028 and remain level thereafter. The selection of a discount rate is made annually and is selected by the Company based upon comparison of the expected future cash flows associated with the Company’s future payments under its consolidated postretirement obligations to a yield curve created using high quality bonds that closely match those expected future cash flows. This rate decreased during 2020 due to market conditions. The assumed healthcare trend rate is also reviewed at least annually and is determined based upon both historical experience with the Company’s healthcare benefits paid and expectations of how those trends may or may not change in future years.

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The components of deferred tax assets and liabilities at December 31, 2020 and 2019, are as follows: (in millions) 2020 2019 DEFERRED TAX LIABILITIES: Accelerated depreciation $ 2,939 $ 3,096 Prepaid insurance 190 12 Operating lease right-of-use assets 423 293 Other 67 81 Total deferred tax liabilities 3,619 3,482 DEFERRED TAX ASSETS: Accrued employee benefits 491 346 Rapid rewards loyalty liability 632 305 Operating lease liabilities 443 308 Residual travel funds 117 — Construction obligation 72 38 Net operating losses and tax credits 60 (a) 8 Other 170 113 Total deferred tax assets 1,985 1,118 Net deferred tax liability $ 1,634 $ 2,364 (a) At December 31, 2020, the Company had approximately $852 million of state net operating loss carryforwards to reduce future state taxable income. These state net operating loss carryforwards will expire in years 2025 - 2040 if unused. The Company's income tax benefit recorded was 27.8 percent for 2020, which is higher than its tax rate of 22.2 percent for 2019. The higher effective tax rate in 2020 reflects the benefit of carrying back 2020 net losses to claim tax refunds against previous cash taxes paid relating to tax years 2015 through 2019, some of which were at higher rates than the current year. The provision (benefit) for income taxes is composed of the following: (in millions) 2020 2019 2018 CURRENT: Federal (a) $ (273) $ 610 $ 338 State (5) 102 60 Change in federal statutory rate (b) (188) — — Total current (466) 712 398 DEFERRED: Federal (a) (589) (18) 299 State (76) (6) 2 State net operating losses (51) — — Change in federal statutory tax rate (c) — (31) — Total deferred (716) (55) 301 $ (1,182) $ 657 $ 699 (a) The CARES Act allows entities to carry back 2020 losses to prior periods of up to five years, and claim refunds of federal taxes paid, and the Company expects to receive a significant cash tax refund once it completes all the necessary requirements to make the appropriate filings with the IRS. (b) The benefit is representative of the excess refund generated as the result of carrying the 2020 losses back to a period when the federal statutory tax rate was 35 percent as opposed to the current tax rate of 21 percent. (c) The Tax Cuts and Jobs Act was enacted in December 2017, which reduced the U.S. federal corporate tax rate from the previous rate of 35 percent to 21 percent. The effective tax rate on Income (loss) before income taxes differed from the federal income tax statutory rate for the following reasons: (in millions) 2020 2019 2018 Tax at statutory U.S. tax rates $ (894) $ 621 $ 664 State income taxes, net of federal benefit (115) 76 49 Change in federal statutory tax rate (188) (a) (31) (b) — Other, net 15 (9) (14) Total income tax provision (benefit) $ (1,182) $ 657 $ 699 (a) The benefit is representative of the excess refund generated as the result of carrying the 2020 losses back to a period when the federal statutory tax rate was 35 percent as opposed to the current tax rate of 21 percent. (b) The Tax Cuts and Jobs Act was enacted in December 2017, which reduced the U.S. federal corporate tax rate from the previous rate of 35 percent to 21 percent. The only periods subject to examination for the Company’s federal tax return are the 2019 and 2020

SUPPLEMENTAL FINANCIAL INFORMAT

SUPPLEMENTAL FINANCIAL INFORMATION	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block [Abstract]
SUPPLEMENTAL FINANCIAL INFORMATION	SUPPLEMENTAL FINANCIAL INFORMATION (in millions) December 31, 2020 December 31, 2019 Trade receivables $ 46 $ 53 Credit card receivables 35 112 Business partners and other suppliers 274 779 Taxes receivable 740 (a) 87 Other 35 55 Accounts and other receivables $ 1,130 $ 1,086 (in millions) December 31, 2020 December 31, 2019 Derivative contracts $ 90 $ 49 Intangible assets, net 295 296 Other 337 232 Other assets $ 722 $ 577 (in millions) December 31, 2020 December 31, 2019 Accounts payable trade $ 111 $ 304 Salaries payable 201 231 Taxes payable excluding income taxes 49 227 Aircraft maintenance payable 95 162 Fuel payable 66 129 Dividends payable — 93 Other payable 409 428 Accounts payable $ 931 $ 1,574 (in millions) December 31, 2020 December 31, 2019 Extended Emergency Time Off $ 393 $ — Voluntary Separation Program 2020 143 — Profitsharing and savings plans 25 695 Vendor prepayment 600 (b) — Vacation pay 436 434 Health 111 120 Workers compensation 161 166 Property and income taxes 84 79 Interest 49 16 Other 257 239 Accrued liabilities $ 2,259 $ 1,749 (in millions) December 31, 2020 December 31, 2019 Extended Emergency Time Off $ 57 $ — Voluntary Separation Program 2020 321 — Postretirement obligation 428 288 Other deferred compensation 353 313 Other 88 105 Other noncurrent liabilities $ 1,247 $ 706 (a) This amount includes approximately $470 million associated with a significant cash tax refund expected as a result of the CARES Act allowing entities to carry back 2020 losses to prior periods of up to five years, and claim refunds of federal taxes paid. This amount also includes excise taxes remitted to taxing authorities for which the subsequent flights were canceled by Customers, resulting in amounts due back to the Company. See Note 15 for further information. (b) In fourth quarter 2020, the Company received a $600 million prepayment from Chase for Rapid Rewards points expected to be purchased during 2021, based on cardholder activity on its Visa card associated with its loyalty program. The Company currently expects the majority of this amount to be reclassified to deferred revenue in Air Traffic liability--loyalty during the first half of 2021. For further information on supplier receivables, see Note 17. For further information on fuel derivative and interest rate derivative contracts, see Note 11. Other Operating Expenses Other operating expenses consist of aircraft rentals, distribution costs, advertising expenses, personnel expenses, professional fees, and other operating costs, none of which individually exceed 10 percent of Operating expenses.

BOEING 737 MAX AIRCRAFT GROUNDI

BOEING 737 MAX AIRCRAFT GROUNDING	12 Months Ended
	Dec. 31, 2020
Unusual or Infrequent Items, or Both [Abstract]
Boeing 737 MAX Aircraft Grounding	BOEING 737 MAX AIRCRAFT GROUNDING AND RETURN TO SERVICE On March 13, 2019, the FAA issued an emergency order for all U.S. airlines to ground all Boeing MAX aircraft. The Company immediately complied with the order and grounded all 34 MAX aircraft in its fleet. On November 18, 2020, the FAA rescinded the emergency order and issued official requirements to enable U.S. airlines to return the Boeing 737 MAX to service. The most significant financial impacts of the grounding to the Company were the lost revenues, operating income, and operating cash flows, and delayed capital expenditures, directly associated with its grounded MAX fleet and other new aircraft that have not been able to be delivered. In July 2019, the Boeing Company announced a $4.9 billion after-tax charge for "potential concessions and other considerations to customers for disruptions related to the 737 MAX grounding." In January 2020, the Boeing Company announced an additional pre-tax charge of $2.6 billion related to "estimated potential concessions and other considerations to customers related to the 737 MAX grounding." During fourth quarter 2019, the Company entered into a Memorandum of Understanding with Boeing to compensate Southwest for estimated financial damages incurred during 2019 related to the grounding of the MAX. The terms of the agreement are confidential, but are intended to provide for a substantial portion of the Company’s financial damages associated with both the 34 MAX aircraft that were grounded as of March 13, 2019, as well as the 41 additional MAX aircraft the Company was scheduled to receive (28 owned MAX from Boeing and 13 leased MAX from third parties) from March 13, 2019 through December 31, 2019. In accordance with applicable accounting principles, the Company will account for substantially all of the proceeds received from Boeing as a reduction in cost basis spread across both the existing owned MAX in the Company’s fleet at the time, plus the Company’s future firm aircraft deliveries as of the date of the agreement. No material financial impacts of the agreement were realized in the Company’s earnings during the years ended December 31, 2019 and 2020. A total of $428 million in proceeds received in cash from Boeing are reflected within Investing Activities in the Consolidated Statement of Cash Flows for the year ended December 31, 2020. The Company is currently working to meet the FAA's official requirements to enable airlines to return the Boeing 737 MAX to service by modifying certain operating procedures, implementing enhanced Pilot training requirements, installing FAA-approved flight control software updates, and completing other required maintenance tasks specific to the MAX aircraft. The Company has scheduled the MAX return to revenue service on March 11, 2021, after the Company is expected to have met all FAA requirements and all active Pilots are expected to have received updated, MAX-related training. During December 2020, the Company took delivery of seven new leased MAX aircraft from third parties.

QUARTERLY FINANCIAL DATA

QUARTERLY FINANCIAL DATA	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Data [Abstract]
QUARTERLY FINANCIAL DATA	QUARTERLY FINANCIAL DATA (unaudited) Three months ended (in millions except per share amounts) March 31 June 30 Sept. 30 Dec. 31 2020 Operating revenues $ 4,234 $ 1,008 $ 1,793 $ 2,013 Operating income (loss) (110) (1,127) (1,411) (1,169) Income (loss) before income taxes (144) (1,239) (1,542) (1,331) Net income (loss) (94) (915) (1,157) (908) Net income (loss) per share, basic (0.18) (1.63) (1.96) (1.54) Net income (loss) per share, diluted (0.18) (1.63) (1.96) (1.54) March 31 June 30 Sept. 30 Dec. 31 2019 Operating revenues $ 5,149 $ 5,909 $ 5,639 $ 5,729 Operating income 505 968 819 665 Income before income taxes 504 968 819 666 Net income 387 741 659 514 (a) Net income per share, basic 0.70 1.37 1.24 0.98 (a) Net income per share, diluted 0.70 1.37 1.23 0.98 (a)

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
New Accounting Pronouncements, Policy	On August 5, 2020, the Financial Accounting Standards Board (the "FASB") issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity. This new standard reduces the number of accounting models for convertible debt instruments and convertible preferred stock, enhances information transparency by making targeted improvements to the disclosures for convertible instruments and earnings-per-share (EPS) guidance, and amends the guidance for the derivatives scope exception for contracts in an entity’s own equity to reduce form-over-substance-based accounting conclusions. This standard is effective for fiscal years beginning after December 15, 2021. Companies may elect early adoption for periods beginning after December 15, 2020. The FASB specified that an entity should adopt the guidance as of the beginning of its annual fiscal year. The Company is evaluating this new standard and plans to provide additional information about its expected impact on the Company's financial statements and disclosures at a future date. On December 18, 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. This new standard eliminates certain exceptions in ASC 740 related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period, and the recognition of deferred tax liabilities for outside basis differences. It also clarifies and simplifies other aspects of the accounting for income taxes. This standard is effective for fiscal years, and interim periods within those years, beginning after December 15, 2020, with early adoption permitted in any interim period within that year. The Company elected to early adopt this standard as of January 1, 2020. The most significant impact to the Company is the removal of a limit on the tax benefit recognized on pre-tax losses in interim periods. However, the early adoption as of January 1, 2020, did not have an impact on the Company's financial statements or disclosures for 2020. On August 29, 2018, the FASB issued ASU No. 2018-15, Intangibles—Goodwill and Other—Internal-Use Software. This standard requires a customer in a cloud computing arrangement that is a service contract to follow the internal-use software guidance in ASC 350-40, Accounting for Internal-Use Software, to determine which implementation costs to (i) capitalize as assets and amortize over the term of the hosting arrangement or (ii) expense as incurred. This standard is effective for public business entities in fiscal years beginning after December 15, 2019, and the standard was adopted and applied prospectively by the Company as of January 1, 2020, but it did not have a significant impact on the Company's financial statements and disclosures. On August 28, 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement. This standard is effective for public business entities in fiscal years beginning after December 15, 2019, and for interim periods within those fiscal years. This standard requires changes to the disclosure requirements for fair value measurements for certain Level 3 items, and specifies that some of the changes must be applied prospectively, while others should be applied retrospectively. The Company adopted the standard as of January 1, 2020, but it did not have a significant impact on the Company's financial statements or disclosures. See Note 12 for further information on the Company's fair value measurements. On January 26, 2017, the FASB issued ASU No. 2017-04, Simplifying the Test for Goodwill Impairment. The new standard eliminates Step 2 from the goodwill impairment test. An entity should recognize a goodwill impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value. This standard is effective for public business entities in fiscal years beginning after December 15, 2019, and the standard was adopted and applied prospectively by the Company as of January 1, 2020, but it did not have a significant impact on the Company's financial statements and disclosures. On June 16, 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments. The new standard requires the use of an “expected loss” model on certain types of financial instruments. The standard also amends the impairment model for available-for-sale debt securities and requires estimated credit losses to be recorded as allowances instead of reductions to amortized cost of the securities. This standard is effective for public business entities in fiscal years beginning after December 15, 2019, and the standard was adopted and applied prospectively by the Company as of January 1, 2020, but it did not have a significant impact on the Company's financial statements and disclosures. On February 25, 2016, the FASB issued the New Lease Standard. The New Lease Standard requires lessees to recognize a right-of-use asset and a lease liability on the balance sheet for all leases (with the exception of short-term leases, as defined in the New Lease Standard) at the lease commencement date and recognize expenses on the income statement in a similar manner to the legacy guidance in ASC 840, Leases ("ASC 840"). The Company adopted the provisions of the New Lease Standard effective January 1, 2019, using the modified retrospective adoption method, utilizing the simplified transition option available in the New Lease Standard, which allows entities to continue to apply the legacy guidance in ASC 840, including its disclosure requirements, in the comparative periods presented in the year of adoption. The Company elected the package of practical expedients available under the transition provisions of the New Lease Standard, including (i) not reassessing whether expired or existing contracts contain leases, (ii) not reassessing lease classification, and (iii) not revaluing initial direct costs for existing leases.
Basis of Presentation	Basis of Presentation Southwest Airlines Co. (the "Company") operates Southwest Airlines, a major domestic airline. The Consolidated Financial Statements include the accounts of the Company and its wholly owned subsidiaries, which include AirTran Holdings, LLC, the successor to AirTran Holdings, Inc. ("AirTran Holdings"), the former parent company of AirTran Airways, Inc., and Triple Crown Assurance Co., an insurance captive. The accompanying Consolidated Financial Statements include the results of operations and cash flows for all periods presented and all significant inter-entity balances and transactions have been eliminated. The preparation of financial statements in conformity with generally accepted accounting principles in the United States ("GAAP") requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from these estimates. Effective as of January 1, 2019, the Company adopted Accounting Standards Update ("ASU") No. 2016-02, Leases,
Cash and cash equivalents	Cash and Cash Equivalents Cash in excess of that necessary for operating requirements is invested in short-term, highly liquid, income-producing investments. Investments with original maturities of three months or less when purchased are classified as cash and cash equivalents, which primarily consist of certificates of deposit, money market funds, and investment grade commercial paper issued by major corporations and financial institutions. Cash and cash equivalents are stated at cost, which approximates fair value. As of December 31, 2020 and 2019, $34 million and $25 million, respectively, in cash collateral deposits were held by the Company from its fuel hedge counterparties, and no cash collateral deposits were held by or provided by the Company to its interest rate hedge counterparties for both periods. Cash collateral amounts provided or held associated with fuel and interest rate derivative instruments are not restricted in any way and earn interest income at an agreed upon rate that approximates the rates earned on short-term securities issued by the U.S. Government. Depending on the fair value of the Company’s fuel and interest rate derivative instruments, the amounts of collateral deposits held or provided at any point in time can fluctuate significantly. See Note 11 for further information on these collateral deposits and fuel derivative instruments.
Short-term and noncurrent investments	Short-term and Noncurrent Investments Short-term investments consist of investments with original maturities of greater than three months but less than twelve months when purchased. These are primarily short-term securities issued by the U.S. Government and certificates of deposit issued by domestic banks. All of these investments are classified as available-for-sale securities and are stated at fair value, which approximates cost. For all short-term investments, at each reset period or upon reinvestment, the Company accounts for the transaction as Proceeds from sales of short-term investments for the security relinquished, and Purchases of short-investments for the security purchased, in the accompanying Consolidated Statement of Cash Flows. Unrealized gains and losses, net of tax, if any, are recognized in Accumulated other comprehensive income (loss) ("AOCI") in the accompanying Consolidated Balance Sheet. Realized net gains and losses on specific investments, if any, are reflected in Interest income in the accompanying Consolidated Statement of Income (Loss). Both unrealized and realized gains and/or losses associated with investments were immaterial for all years presented.
Accounts and other receivables	Accounts and Other Receivables Accounts and other receivables are initially recorded at cost and are evaluated for collectability in every period. They primarily consist of the amounts due from the Company's business partners and other suppliers, amounts due from business partners in the Company’s loyalty program, and tax receivables from overpayment or net operating losses that are allowed to be carried back to prior periods to claim refunds against prior taxes paid. See Note 16 for further information. The allowance for doubtful accounts was immaterial at December 31, 2020 and 2019. In addition, the provision for doubtful accounts and write-offs for 2020, 2019, and 2018 were each immaterial.
Inventories	Inventories Inventories primarily consist of aircraft fuel, flight equipment expendable parts, materials, and supplies. All of these items are carried at average cost, less an allowance for obsolescence. These items are generally charged to expense when issued for use. The reserve for obsolescence was immaterial at December 31, 2020, and 2019. In addition, the Company’s provision for obsolescence and write-offs for 2020, 2019, and 2018 were each immaterial.
Property and equipment	Property and Equipment Property and equipment is stated at cost. Capital expenditures include payments made for aircraft, other flight equipment, purchase deposits related to future aircraft deliveries, airport and other facility construction projects, and ground and other property and equipment. Depreciation is provided by the straight-line method to estimated residual values over periods of approximately 25 years for flight equipment, and 5 to 30 years for ground property and equipment. Residual values estimated for aircraft are approximately 15 percent, and generally range from 0 to 10 percent for ground property and equipment. Assets constructed for others consists of airport improvement projects in which the Company is considered to have control of the asset during the construction period. Once construction is effectively completed, the sale-leaseback model would apply when control passes from the lessee to the lessor. See Note 5 for further information. The Company evaluates its long-lived assets used in operations for impairment when events and circumstances indicate that the undiscounted cash flows to be generated by that asset are less than the carrying amounts of the asset and may not be recoverable. Factors that would indicate potential impairment include, but are not limited to, significant decreases in the market value of the long-lived asset(s), a significant change in the long-lived asset’s physical condition, and operating or cash flow losses associated with the use of the long-lived asset. If an asset is deemed to be impaired, an impairment loss is recorded for the excess of the asset book value in relation to its estimated fair value. As a result of the events and impacts surrounding the COVID-19 pandemic, including the Company's net loss incurred during the year ended December 31, 2020, and the significant number of aircraft that have been placed in storage, the Company assessed whether any impairment of its amortizable assets existed. No aircraft impairment charges were deemed necessary for the majority of 2020. For the purpose of impairment assessment, the Company evaluates its all Boeing fleet as one asset group. However, during fourth quarter 2020, the Company made the decision to permanently ground, and accelerate the retirement of, 20 of its 737-700 aircraft as of December 31, 2020. This action resulted in the Company recording $32 million in impairment charges associated with these 20 aircraft.
Leases	Leases The Company determines if an arrangement is a lease at inception. Operating leases are included in Operating lease right-of-use assets, Current operating lease liabilities, and Noncurrent operating lease liabilities in the Consolidated Balance Sheet. Finance leases are included in Property and equipment, Current maturities of long-term debt, and Long-term debt less current maturities in the Consolidated Balance Sheet.
Aircraft and engine maintenance	Aircraft and Engine Maintenance The cost of scheduled inspections and repairs and routine maintenance costs for all aircraft and engines are charged to Maintenance materials and repairs expense within the accompanying Consolidated Statement of Income (Loss) as incurred. The Company has maintenance agreements related to certain of its aircraft engines with external service providers, including agreements that effectively transfer the risk of performance of such work to the service provider. Under the agreements where the risk of performance is deemed transferred to the counterparty, the appropriate expense is recorded commensurate with the period in which the corresponding level of service is provided. Generally, expense is recorded on a straight-line basis over the term of the agreement based on the Company's best estimate of expected future aircraft utilization. For its engine maintenance contracts that do not transfer risk to the service provider, the Company records expense on a time and materials basis when an engine repair event takes place. Modifications that significantly enhance the operating performance or extend the useful lives of aircraft or engines are capitalized and amortized over the remaining life of the asset.
Goodwill and intangible assets	Goodwill and Intangible Assets The Company applies a fair value based impairment test to the carrying value of goodwill and indefinite-lived intangible assets annually on October 1st, or more frequently if certain events or circumstances indicate that an impairment loss may have been incurred. The Company assesses the value of goodwill and indefinite-lived intangible assets under either a qualitative or quantitative approach. Under a qualitative approach, the Company considers various market factors, including applicable key assumptions also used in the quantitative assessment listed below. These factors are analyzed to determine if events and circumstances could reasonably have affected the fair value of goodwill and indefinite-lived intangible assets. If the Company determines that it is more likely than not that an indefinite-lived intangible asset or reporting unit goodwill is impaired, the quantitative approach is used to assess the asset or reporting unit fair value and the amount of the impairment. Under a quantitative approach, the fair value of the Company's indefinite-lived intangible asset or reporting unit is calculated based on key market participant assumptions. If the indefinite-lived intangible assets' carrying value exceeds the fair value calculated using the quantitative approach, an impairment charge is recorded for the difference in fair value and carrying value. If the reporting unit carrying value exceeds the reporting unit fair value calculated using the quantitative approach, an impairment charge is recorded for the difference between fair value and carrying value, limited to the amount of goodwill in the reporting unit. When performing a quantitative impairment assessment of goodwill and indefinite-lived intangible assets, fair value is estimated based on (i) recent market transactions, where available, (ii) projected discounted cash flows (an income approach), or (iii) a combination of limited market transactions and the lease savings method (which reflects potential annual after-tax lease savings arising from owning the certain indefinite-lived intangibles rather than leasing them from another airline at market rates). The Company applied the quantitative approach during its annual 2020 impairment tests. Key assumptions and/or estimates made in the Company's 2020 impairment tests included the following: (i) a projection of revenues, expenses, and cash flows; (ii) terminal period revenue growth and cash flows; (iii) an estimated weighted average cost of capital; (iv) an assumed discount rate depending on the asset; (v) a tax rate; and (vi) market purchase prices and lease rates for comparable assets. The Company believes these assumptions are consistent with those a hypothetical market participant would use given circumstances that were present at the time the estimates were made. However, actual results and amounts may be significantly different from the Company's estimates. As a result of the annual impairment tests performed as of October 1, 2020, no impairment was determined to exist for Goodwill or indefinite-lived intangible assets, as the fair values of the reporting unit and indefinite-lived intangible assets exceeded their respective carrying values. The Company’s intangible assets primarily consist of acquired rights to certain airport owned takeoff and landing slots (a "slot" is the right of an air carrier, pursuant to regulations of the Federal Aviation Administration ("FAA"), to operate a takeoff or landing at a specific time at certain airports) at certain domestic slot-controlled airports. Indefinite lived slots of $295 million are included as a component of Other assets in the Company's Consolidated Balance Sheet, as of December 31, 2020 and 2019.
Revenue recognition	Revenue Recognition Tickets sold are initially deferred as Air traffic liability. Passenger revenue is recognized and Air traffic liability is reduced when transportation is provided. Air traffic liability primarily represents tickets sold for future travel dates, funds that are past flight date and remain unused, but are expected to be used in the future, and the Company’s liability for loyalty benefits that are expected to be redeemed in the future. The majority of the Company’s tickets sold are nonrefundable. Southwest has a No Show policy that applies to fares that are not canceled or changed by a Customer at least ten minutes prior to a flight's scheduled departure. Nonrefundable tickets that are sold but not flown on the travel date, and are canceled in accordance with the No Show policy, can be applied to future travel. Refundable tickets that are sold but not flown on the travel date can also be applied to future travel. A small percentage of tickets (or partial tickets) expire unused. The Company estimates the amount of tickets that expire unused and recognizes such amounts in Passenger revenue once the scheduled flight date has lapsed in proportion to the pattern of flights taken by the Customers. Based on the Company's revenue recognition policy, revenue is recorded at the flight date for a Customer who does not change his/her itinerary and loses his/her funds as the Company has then fulfilled its performance obligation. Amounts collected from passengers for ancillary services are also recognized when the service is provided, which is typically the flight date. Initial spoilage estimates for both tickets and funds available for future use are routinely adjusted and ultimately finalized once the tickets expire, which is typically twelve months after the original purchase date. However, during 2020, the Company extended the expiration dates for a significant amount of tickets and funds beyond its normal twelve months. Spoilage estimates are based on the Company's Customers' historical travel behavior as well as assumptions about the Customers' future travel behavior. Assumptions used to generate spoilage estimates can be impacted by several factors including, but not limited to: fare increases, fare sales, changes to the Company's ticketing policies, changes to the Company’s refund, exchange, and unused funds policies, seat availability, and economic factors. Given the unprecedented amount of 2020 Customer flight cancellations and the amount of travel funds provided, the Company expects additional variability in the amount of spoilage revenue recorded in future periods, as the estimates of the portion of sold tickets that will expire unused may differ from historical experience. See Note 6 for further information. Approximately $184 million, approximately $615 million, and approximately $566 million of the Company's Operating revenues in 2020, 2019, and 2018, respectively, were attributable to foreign operations. The remainder of In order to determine the value of each loyalty point, certain assumptions must be made at the time of measurement, which include the following: • Allocation of Passenger Revenue - Revenues from Passengers, related to travel, who also earn Rapid Rewards Points have been allocated between flight (recognized as revenue when transportation is provided) and Rapid Rewards Points (deferred until points are redeemed) based on each obligation’s relative standalone selling price. The Company utilizes historical earning patterns to assist in this allocation. • Fair Value of Rapid Rewards Points - Determined from the base fare value of tickets which were purchased using prior point redemptions for travel and other products and services, which the Company believes to be indicative of the fair value of points as perceived by Customers and representative of the value of each point at the time of redemption. The Company’s booking site allows a Customer to toggle between fares utilizing either cash or point redemptions, which provides the Customer with an approximation of the equivalent value of their points. The value can differ, however, based on demand, the amount of time prior to the flight, and other factors. The fare mix during the period measured represents a constraint, which could result in the assumptions above changing at the measurement date, as fare classes can have different coefficients used to determine the total loyalty points needed to purchase an award ticket. The mixture of these fare classes and changes in the coefficients used by the Company could cause the fair value per point to increase or decrease. For points that are expected to remain unused, the Company recognizes spoilage in proportion to the pattern of points used by the Customer, which approximates the average period over which the population of Rapid Reward Members redeem their points. The Company utilizes historical behavioral data to develop a predictive statistical model to analyze the amount of spoilage expected for points sold to business partners and earned through flight. The Company continues to evaluate expected spoilage annually and applies appropriate adjustments in the fourth quarter of each year, or other times, if changes in Customer behavior are detected. Changes to spoilage estimates impact revenue recognition prospectively. Due to the size of the Company’s liability for loyalty benefits, changes in Customer behavior and/or expected future redemption patterns could result in significant variations in Passenger revenue. All performance obligations related to freight services sold are completed within twelve months or less; therefore, the Company has elected to not disclose the amount of the remaining transaction price and its expected timing of recognition for freight shipments. Other revenues primarily consist of marketing royalties associated with the Company’s co-branded Chase ® Visa credit card, but also include commissions and advertising associated with Southwest.com ® . All amounts classified as Other revenues are paid monthly, coinciding with the Company fulfilling its deliverables; therefore, the Company has elected to not disclose the amount of the remaining transaction price and its expected timing of recognition for such services provided.
Loyalty program	Loyalty ProgramThe Company records a liability for the relative fair value of providing free travel under its loyalty program for all points earned from flight activity or sold to companies participating in the Company’s Rapid Rewards loyalty program as business partners that are expected to be redeemed for future travel. The loyalty liability represents performance obligations that will be satisfied when a Rapid Rewards loyalty member redeems points for travel or other goods and services. Points earned from flight activity are valued at their relative standalone selling price by applying fair value based on historical redemption patterns. Points earned from business partner activity, which primarily consist of points sold, along with related marketing services, to companies participating in the Rapid Rewards loyalty program, are valued using a relative fair value methodology based on the contractual rate which partners pay to Southwest to award Rapid Rewards points to the business partner’s customers. For points that are expected to remain unused, the Company recognizes spoilage in proportion to the pattern of points used by the Customer, which approximates the average period over which the population of Rapid Reward Members redeem their points. The Company records passenger revenue related to air transportation when the transportation is delivered. The marketing elements are recognized as Other - net revenue when earned. The Company’s liability for loyalty benefits includes a portion that is expected to be redeemed during the following twelve months (classified as a component of Air traffic liability), and a portion that is not expected to be redeemed during the following twelve months (classified as Air traffic liability - noncurrent). The Company continually updates this analysis and adjusts the split between current and non-current liabilities as appropriate. See Note 6 for further information.
Advertising	Advertising Advertising costs are charged to expense as incurred. Advertising and promotions expense for the years ended December 31, 2020, 2019, and 2018 was $156 million, $212 million, and $215 million, respectively, and is included as a component of Other operating expense in the accompanying Consolidated Statement of Income (Loss).
Share-based Employee compensation	Share-based Employee Compensation The Company has share-based compensation plans covering certain Employees, including a plan that also covers the Company’s Board of Directors. The Company accounts for share-based compensation based on its grant date fair value. See Note 10 for further information.
Fair Value of Financial Instruments	Financial Derivative Instruments The Company accounts for financial derivative instruments at fair value and applies hedge accounting rules where appropriate. The Company utilizes various derivative instruments, including jet fuel, crude oil, unleaded gasoline, and heating oil-based derivatives, to attempt to reduce the risk of its exposure to jet fuel price increases. These instruments are accounted for as cash flow hedges upon proper qualification. The Company also has had interest rate swap agreements to convert certain floating-rate debt to a fixed-rate and had interest rate swap agreements to convert portions of its fixed-rate debt to floating rates. The Company has forward-stating interest rate swap agreements, the primary objective of which is to hedge forecasted debt issuances. These interest rate hedges are appropriately designated as cash flow hedges. Since the majority of the Company’s financial derivative instruments are not traded on a market exchange, the Company estimates their fair values. Depending on the type of instrument, the values are determined by the use of present value methods or option value models with assumptions about commodity prices based on those observed in underlying markets. All cash flows associated with purchasing and selling derivatives are classified as operating cash flows in the Consolidated Statement of Cash Flows, within Changes in certain assets and liabilities. The Company classifies its Accounting standards pertaining to fair value measurements establish a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value. These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions. As of December 31, 2020, the Company held certain items that are required to be measured at fair value on a recurring basis. These included cash equivalents, short-term investments (primarily treasury bills and certificates of deposit), interest rate derivative contracts, fuel derivative contracts, and available-for-sale securities. The majority of the Company’s short-term investments consist of instruments classified as Level 1. However, the Company has certificates of deposit, commercial paper, and time deposits that are classified as Level 2, due to the fact that the fair value for these instruments is determined utilizing observable inputs in non-active markets. Other available-for-sale securities primarily consist of investments associated with the Company’s excess benefit plan. The Company’s fuel and interest rate derivative instruments consist of over-the-counter contracts, which are not traded on a public exchange. Fuel derivative instruments currently consist solely of option contracts, whereas interest rate derivatives consist solely of swap agreements. See Note 11 for further information on the Company’s derivative instruments and hedging activities. The fair values of swap contracts are determined based on inputs that are readily available in public markets or can be derived from information available in publicly quoted markets. Therefore, the Company has categorized these swap contracts as Level 2. The Company’s Treasury Department, which reports to the Chief Financial Officer, determines the value of option contracts utilizing an option pricing model based on inputs that are either readily available in public markets, can be derived from information available in publicly quoted markets, or are provided by financial institutions that trade these contracts. The option pricing model used by the Company is an industry standard model for valuing options and is the same model used by the broker/dealer community (i.e., the Company’s counterparties). The inputs to this option pricing model are the option strike price, underlying price, risk free rate of interest, time to expiration, and volatility. Because certain inputs used to determine the fair value of option contracts are unobservable (principally implied volatility), the Company has categorized these option contracts as Level 3. Volatility information is obtained from external sources, but is analyzed by the Company for reasonableness and compared to similar information received from other external sources. The fair value of option contracts considers both the intrinsic value and any remaining time value associated with those derivatives that have not yet settled. The Company also considers counterparty credit risk and its own credit risk in its determination of all estimated fair values. To validate the reasonableness of the Company’s option pricing model, on a monthly basis, the Company compares its option valuations to third party valuations. If any significant differences were to be noted, they would be researched in order to determine the reason. However, historically, no significant differences have been noted. The Company has consistently applied these valuation techniques in all periods presented and believes it has obtained the most accurate information available for the types of derivative contracts it holds.
Software capitalization	Software Capitalization The Company capitalizes certain internal and external costs related to the acquisition and development of internal use software during the application development stages of projects. The Company amortizes these costs using the straight-line method over the estimated useful life of the software, which is typically five
Insurance reserves	Insurance Reserves The Company uses a combination of insurance and self-insurance mechanisms, including a wholly-owned captive insurance entity and participation in a reinsurance treaty, to provide for the potential liabilities associated with certain risks, including workers’ compensation, healthcare benefits, general liability, and aviation liability. Liabilities associated with the risks that are retained by the Company are not discounted and are estimated, in part, by considering historical claims experience, demographics, exposure and severity factors and other actuarial assumptions.
Income taxes	Income Taxes The Company accounts for deferred income taxes utilizing an asset and liability method, whereby deferred tax assets and liabilities are recognized based on the tax effect of temporary differences between the financial statements and the tax basis of assets and liabilities, as measured by current enacted tax rates. The Company also evaluates the need for a valuation allowance to reduce deferred tax assets to estimated recoverable amounts. The Company’s policy for recording interest and penalties associated with uncertain tax positions is to record such items as a component of Income (loss) before income taxes. Penalties are recorded in Other (gains) losses, net, and interest paid or received is recorded in Interest expense or Interest income, respectively, in the accompanying Consolidated Statement of Income (Loss). There were no material amounts recorded for penalties and interest related to uncertain tax positions for all years presented. See Note 15 for further information.
Concentration risk	Concentration Risk Approximately 83 percent of the Company’s full-time equivalent Employees are unionized and are covered by collective-bargaining agreements. A percentage of the Company's unionized Employees, including its Pilots, Flight Attendants, Customer Service Agents, Dispatchers, Aircraft Appearance Technicians, and Meteorologists, which had contracts that became amendable on or before December 31, 2020, are in discussions on labor agreements. Those unionized Employee groups in discussions represent approximately 55 percent of the Company’s full-time equivalent Employees as of December 31, 2020. The Company attempts to minimize its concentration risk with regards to its cash, cash equivalents, and its investment portfolio. This is accomplished by diversifying and limiting amounts among different counterparties, the type of investment, and the amount invested in any individual security or money market fund. To manage risk associated with financial derivative instruments held, the Company selects and will periodically review counterparties based on credit ratings, limits its exposure to a single counterparty, and monitors the market position of the program and its relative market position with each counterparty. The Company also has agreements with counterparties containing early termination rights and/or bilateral collateral provisions whereby security is required if market risk exposure exceeds a specified threshold amount or credit ratings fall below certain levels. Collateral deposits provided to or held from counterparties serve to decrease, but not totally eliminate, the credit risk associated with the Company’s hedging program. See Note 11 for further information. As of December 31, 2020, the Company operated an all-Boeing fleet, all of which are variations of the Boeing 737. The Boeing 737 MAX aircraft ("MAX") are crucial to the Company’s growth plans and fleet modernization initiatives. On March 13, 2019, the FAA issued an emergency order for all U.S. airlines to ground the MAX aircraft, including the 34 MAX aircraft in the Company's fleet. On November 18, 2020, the FAA rescinded its order to ground the MAX fleet. The Company is currently working to meet the FAA's requirements by modifying certain operating procedures, implementing enhanced Pilot training requirements, installing FAA-approved flight control software updates, and completing other required maintenance tasks specific to the MAX aircraft. The Company currently estimates that the MAX will return to service on March 11, 2021 after all active Pilots have received updated, MAX-related training. The MAX fleet grounding has adversely affected the Company's operating results, and could have a material adverse effect on the Company's operating results in future periods. Boeing no longer manufactures versions of the 737 other than the 737 MAX family of aircraft. If the 737 MAX aircraft were to again become unavailable for the Company’s flight operations, the Company’s growth would be restricted unless and until it could procure and operate other types of aircraft from Boeing or another manufacturer, seller, or lessor, and the Company’s operations would be materially adversely affected. In particular, if the Company’s growth were to be dependent upon the introduction of a new aircraft make and model to the Company’s fleet, the Company would need to, among other things, (i) develop and implement new maintenance, operating, and training programs, (ii) secure extensive regulatory approvals, and (iii) implement new technologies. The requirements associated with operating a new aircraft make and model could take an extended period of time to fulfill and would likely impose substantial costs on the Company. A shift away from a single fleet type could also add complexity to the Company’s operations, present operational and compliance risks, and materially increase the Company's costs. Any of these events would have a material, adverse effect on the Company's business, operating results, and financial condition. The Company could also be materially adversely affected if the pricing or operational attributes of its aircraft were to become less competitive. See Note 17 for further information. The Company is also dependent on sole or limited suppliers for aircraft engines and certain other aircraft parts and services and would, therefore, also be materially adversely impacted in the event of the unavailability of, inadequate support for, or a mechanical or regulatory issue associated with, engines and other parts. The Company has historically entered into agreements with some of its co-brand, payment, and loyalty partners that contain exclusivity aspects which place certain confidential restrictions on the Company from entering into certain arrangements with other payment and loyalty partners. Some of these agreements automatically renew on an annual basis, unless either party objects to such extension. None of these agreements are more than 10 years in length. The Company believes the financial benefits generated by the exclusivity aspects of these arrangements outweigh the risks involved with such agreements.
Derivatives	Upon proper qualification, the Company accounts for its fuel derivative instruments as cash flow hedges. All periodic changes in fair value of the derivatives designated as hedges are recorded in AOCI until the underlying jet fuel is consumed. See Note 13. The Company's results are subject to the possibility that the derivatives will no longer qualify for hedge accounting, in which case any change in the fair value of derivative instruments since the last reporting period would be recorded in Other (gains) losses, net, in the Consolidated Statement of Income (Loss) in the period of the change; however, any amounts previously recorded to AOCI would remain there until such time as the original forecasted transaction occurs, at which time these amounts would be reclassified to Fuel and oil expense. Factors that have and may continue to lead to the loss of hedge accounting include: significant fluctuation in energy prices, significant weather events affecting refinery capacity and the production of refined products, and the volatility of the different types of products the Company uses in hedging. Increased volatility in these commodity markets for an extended period of time, especially if such volatility were to worsen, could cause the Company to lose hedge accounting altogether for the commodities used in its fuel hedging program, which would create further volatility in the Company’s GAAP financial results. However, even though derivatives may not qualify for hedge accounting, the Company continues to hold the instruments as management believes derivative instruments continue to afford the
Convertible Debt Settlement	Because the Company intends to settle conversions by paying cash up to the principal amount of the Convertible Notes, with any excess conversion value settled in shares of common stock, the Convertible Notes are being accounted for using the treasury stock method for the purposes of Net income (loss) per share. Using this method, the denominator will be affected when the average share price of the Company's common stock for a given period is greater than the conversion price of approximately $38.48 per share. The Convertible Notes stipulated that holders of the notes may not elect to convert their Convertible Notes to shares of common stock until after June 30, 2020, and therefore there was no dilutive impact related to the notes prior to July 1, 2020. As consideration for the Payroll Support funding, the Company agreed to issue Warrants to the Treasury to purchase the Company's common stock in connection with each disbursement of Payroll Support to the Company. The Company accounts for the Warrants using the treasury stock method. Using this method, the denominator will be affected when the average share price of the Company's common stock for a given period is greater than the warrant exercise price of $36.47 per share. While the Company is reporting a net loss, all potential shares are considered antidilutive and have no impact on Net income (loss) per share.
Compensation Related Costs	Grants of RSUs result in the creation of a deferred tax asset, which is a temporary difference, until the time the RSU vests. All excess tax benefits and tax deficiencies are recorded through the income statement. Due to the treatment of RSUs for tax purposes, the Company’s effective tax rate from year to year is subject to variability.
Employee Retirement Plans	Unrecognized prior service cost is expensed using a straight-line amortization of the cost over the average future service of Employees expected to receive benefits under the plans. Actuarial gains are amortized utilizing the minimum amortization method. The following actuarial assumptions were used to account for the Company’s postretirement benefit plans at December 31, 2020, 2019, and 2018: 2020 2019 2018 Weighted-average discount rate 2.45 % 3.30 % 4.35 % Assumed healthcare cost trend rate (a) 6.75 % 7.13 % 7.13 % (a) The assumed healthcare cost trend rate is expected to be 6.50% for 2021, then decline gradually to 4.75% by 2028 and remain level thereafter. The selection of a discount rate is made annually and is selected by the Company based upon comparison of the expected future cash flows associated with the Company’s future payments under its consolidated postretirement obligations to a yield curve created using high quality bonds that closely match those expected future cash flows. This rate decreased during 2020 due to market conditions. The assumed healthcare trend rate is also reviewed at least annually and is determined based upon both historical experience with the Company’s healthcare benefits paid and expectations of how those trends may or may not change in future years.

Net Income (Loss) Per Share (Ta

Net Income (Loss) Per Share (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Schedule Of Earnings Per Share Basic And Diluted	The following table sets forth the computation of basic and diluted net income (loss) per share (in millions except per share amounts). An immaterial number of shares related to the Company's restricted stock units, stock warrants, and convertible notes were excluded from the denominator for fiscal year ended December 31, 2020, because inclusion of such shares would be antidilutive. Year ended December 31, 2020 2019 2018 NUMERATOR: Net income (loss) $ (3,074) $ 2,300 $ 2,465 DENOMINATOR: Weighted-average shares outstanding, basic 565 538 573 Dilutive effect of restricted stock units — 1 1 Adjusted weighted-average shares outstanding, diluted 565 539 574 NET INCOME (LOSS) PER SHARE: Basic $ (5.44) $ 4.28 $ 4.30 Diluted $ (5.44) $ 4.27 $ 4.29

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Passenger Revenue	The following table provides the components of Passenger revenue recognized for the years ended December 31, 2020, 2019, and 2018: Year ended December 31, (in millions) 2020 2019 2018 Passenger non-loyalty $ 6,303 $ 17,578 $ 17,506 Passenger loyalty - air transportation 1,003 2,487 2,307 Passenger ancillary sold separately 359 711 642 Total passenger revenues $ 7,665 $ 20,776 $ 20,455
Components of Air Traffic Liability	As of the years ended December 31, 2020 and 2019, the components of Air traffic liability, including contract liabilities based on tickets sold, unused funds available to the Customer, and loyalty points available for redemption, net of expected spoilage, within the Consolidated Balance Sheet were as follows: Balance as of (in millions) December 31, 2020 December 31, 2019 Air traffic liability - passenger travel and ancillary passenger services $ 2,686 $ 2,125 Air traffic liability - loyalty program 4,447 3,385 Total Air traffic liability $ 7,133 $ 5,510 Year ended December 31, 2020 2019 Air traffic liability - loyalty program - beginning balance $ 3,385 $ 3,011 Amounts deferred associated with points awarded 1,958 2,941 Revenue recognized from points redeemed - Passenger (1,003) (2,487) Revenue recognized from points redeemed - Other (60) (80) Unused funds converted to loyalty points 167 — Air traffic liability - loyalty program - ending balance $ 4,447 $ 3,385
Rollforward of Air Traffic Liability	Air traffic liability includes consideration received for ticket and loyalty related performance obligations which have not been satisfied as of a given date. Rollforwards of the amounts included in Air traffic liability as of December 31, 2020 and 2019 were as follows (in millions): Air traffic liability Balance at December 31, 2019 $ 5,510 Current period sales (passenger travel, ancillary services, flight loyalty, and partner loyalty) 9,348 Revenue from amounts included in contract liability opening balances (2,317) Revenue from current period sales (5,408) Balance at December 31, 2020 $ 7,133 Air traffic liability Balance at December 31, 2018 $ 5,070 Current period sales (passenger travel, ancillary services, flight loyalty, and partner loyalty) 21,296 Revenue from amounts included in contract liability opening balances (3,816) Revenue from current period sales (17,040) Balance at December 31, 2019 $ 5,510

FINANCING ACTIVITIES (Tables)

FINANCING ACTIVITIES (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	(in millions) December 31, 2020 December 31, 2019 737 Aircraft Notes payable through April 2020 $ — $ 20 Term Loan Agreement payable through May 2020 - 5.223% — 134 2.65% Notes due November 2020 — 500 2.75% Notes due 2022 300 300 Pass Through Certificates due 2022 - 6.24% 137 197 4.75% Notes due 2023 1,250 — 1.25% Convertible Notes due 2025 1,945 — 5.25% Notes due 2025 1,550 — Term Loan Agreement payable through 2025 - 1.65% 119 — 3.00% Notes due 2026 300 300 Term Loan Agreement payable through 2026 - 1.34% 159 178 3.45% Notes due 2027 300 300 5.125% Notes due 2027 2,000 — 7.375% Debentures due 2027 119 122 Term Loan Agreement payable through 2028 - 1.65% 184 — 2.625% Notes due 2030 500 — 1.000% Payroll Support Program Loan due 2030 (See Note 2) 976 — Finance leases 542 627 $ 10,381 $ 2,678 Less current maturities 220 819 Less debt discount and issuance costs 50 13 $ 10,111 $ 1,846

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases - Tables [Abstract]
Lease-Related Assets and Liabilities	Lease-related assets and liabilities recorded on the Consolidated Balance Sheet were as follows: (in millions) Balance Sheet location December 31, 2020 December 31, 2019 Assets Operating Operating lease right-of-use assets (net) $ 1,892 $ 1,349 Finance Property and equipment (net of allowance for depreciation and amortization of $567 and $455) 667 779 Total lease assets $ 2,559 $ 2,128 Liabilities Current Operating Current operating lease liabilities $ 306 $ 353 Finance Current maturities of long-term debt 83 85 Noncurrent Operating Noncurrent operating lease liabilities 1,562 978 Finance Long-term debt less current maturities 459 542 Total lease liabilities $ 2,410 $ 1,958
Components of Lease Cost	The components of lease costs, included in the Consolidated Statement of Comprehensive Income (Loss), were as follows: (in millions) Statement of Comprehensive Income (Loss) location Year ended December 31, 2020 Year ended December 31, 2019 Operating lease cost - aircraft (a) Other operating expenses $ 216 $ 182 Operating lease cost - other Landing fees and airport rentals, and Other operating expenses 89 89 Short-term lease cost Other operating expenses 1 4 Variable lease cost Landing fees and airport rentals, and Other operating expenses 1,260 1,377 Finance lease cost: Amortization of lease liabilities Depreciation and amortization 113 116 Interest on lease liabilities Interest expense 22 26 Total net finance lease cost $ 135 $ 142
Schedule of Cash Flow, Supplemental Disclosures	Supplemental cash flow information related to leases, included in the Consolidated Statement of Cash Flows, was as follows: ( in millions ) Year ended December 31, 2020 Year ended December 31, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 398 $ 379 Operating cash flows for finance leases 22 26 Financing cash flows for finance leases 85 85 Right-of-use assets obtained in exchange for lease obligations: Operating leases 915 230 Finance leases — 1
Finance Lease Maturity	As of December 31, 2020, maturities of lease liabilities were as follows: ( in millions ) Operating leases Finance leases 2021 $ 371 $ 102 2022 253 98 2023 219 94 2024 193 90 2025 156 74 Thereafter 1,156 156 Total lease payments $ 2,348 $ 614 Less imputed interest (480) (72) Total lease obligations 1,868 542 Less current obligations (306) (83) Long-term lease obligations $ 1,562 $ 459
Operating Lease Maturity	As of December 31, 2020, maturities of lease liabilities were as follows: ( in millions ) Operating leases Finance leases 2021 $ 371 $ 102 2022 253 98 2023 219 94 2024 193 90 2025 156 74 Thereafter 1,156 156 Total lease payments $ 2,348 $ 614 Less imputed interest (480) (72) Total lease obligations 1,868 542 Less current obligations (306) (83) Long-term lease obligations $ 1,562 $ 459
Lessee Operating and Finance Leases Weighted Average Assumptions	The table below presents additional information related to the Company's leases: Weighted average remaining lease term December 31, 2020 December 31, 2019 Operating leases 10 years 9 years Finance leases 7 years 8 years Weighted average discount rate Operating leases (a) 3.8 % 3.7 % Finance leases 3.8 % 3.8 % (a) Upon adoption of the New Lease Standard, the incremental borrowing rate used for existing leases was established as of January 1, 2019.

Stock Plans (Tables)

Stock Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Schedule of Share-based Compensation, Restricted Stock Units Award Activity	Aggregated information regarding the Company’s RSUs and PBRSUs is summarized below: All Restricted Stock Units Units (000) Wtd. Average Outstanding December 31, 2017 1,294 $ 45.32 Granted 782 (a) 60.80 Vested (670) 45.11 Surrendered (64) 47.05 Outstanding December 31, 2018 1,342 52.56 Granted 994 (b) 57.49 Vested (744) 42.42 Surrendered (47) 57.72 Outstanding December 31, 2019, Unvested 1,545 57.65 Granted 1,235 (c) 56.89 Vested (715) 54.70 Surrendered (103) 58.04 Outstanding December 31, 2020, Unvested 1,962 57.81 (a) Includes 308 thousand PBRSUs (b) Includes 387 thousand PBRSUs (c) Includes 519 thousand PBRSUs
Schedule of Share-based Compensation, Employee Stock Purchase Plan, Activity	The following table provides information about the Company’s ESPP activity during 2020, 2019, and 2018: Employee Stock Purchase Plan (a) Total number Weighted-average of shares Average fair value of each purchased price paid purchase right Year ended (in thousands) per share under the ESPP December 31, 2018 661 $ 50.73 $ 5.64 December 31, 2019 821 $ 47.60 $ 5.29 December 31, 2020 1,386 $ 34.39 $ 3.82

Financial Derivative Instrume_2

Financial Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Volume of Fuel Hedging	The following table provides information about the Company’s volume of fuel hedging on an economic basis: Maximum fuel hedged as of December 31, 2020 Derivative underlying commodity type as of Period (by year) (gallons in millions) (a) December 31, 2020 2021 1,283 WTI crude oil and Brent crude oil 2022 1,220 WTI crude oil and Brent crude oil 2023 643 WTI crude oil and Brent crude oil Beyond 2023 101 WTI crude oil (a) Due to the types of derivatives utilized by the Company and different price levels of those contracts, these volumes represent the maximum economic hedge in place and may vary significantly as market prices and the Company's flight schedule fluctuate.
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	The following table presents the location of all assets and liabilities associated with the Company’s derivative instruments within the Consolidated Balance Sheet: Asset derivatives Liability derivatives Balance Sheet Fair value at Fair value at Fair value at Fair value at (in millions) location 12/31/2020 12/31/2019 12/31/2020 12/31/2019 Derivatives designated as hedges (a) Fuel derivative contracts (gross) Prepaid expenses and other current assets $ 9 $ 48 $ — $ — Fuel derivative contracts (gross) Other assets 121 62 — — Interest rate derivative contracts Other assets — 2 — — Interest rate derivative contracts Accrued liabilities — — — 5 Interest rate derivative contracts Other noncurrent liabilities — — 6 1 Total derivatives designated as hedges $ 130 $ 112 $ 6 $ 6 Derivatives not designated as hedges (a) Fuel derivative contracts (gross) Prepaid expenses and other current assets $ 4 $ — $ — $ — Total derivatives $ 134 $ 112 $ 6 $ 6 (a) Represents the position of each trade before consideration of offsetting positions with each counterparty and does not include the impact of cash collateral deposits provided to or received from counterparties. See discussion of credit risk and collateral following in this Note.
Cash Collateral Deposits Due To Or From Third Parties and Net Unrealized Losses	In addition, the Company had the following amounts associated with fuel derivative instruments and hedging activities in its Consolidated Balance Sheet: Balance Sheet December 31, December 31, (in millions) location 2020 2019 Cash collateral deposits held from counterparties for fuel contracts - current Offset against Prepaid expenses and other current assets $ 3 $ 10 Cash collateral deposits held from counterparties for fuel contracts - noncurrent Offset against Other assets 31 15
Offsetting Assets	The Company has the following recognized financial assets and financial liabilities resulting from those transactions that meet the scope of the disclosure requirements as necessitated by applicable accounting guidance for balance sheet offsetting: Offsetting of derivative assets (in millions) (i) (ii) (iii) = (i) + (ii) (i) (ii) (iii) = (i) + (ii) December 31, 2020 December 31, 2019 Description Balance Sheet location Gross amounts of recognized assets Gross amounts offset in the Balance Sheet Net amounts of assets presented in the Balance Sheet Gross amounts of recognized assets Gross amounts offset in the Balance Sheet Net amounts of assets presented in the Balance Sheet Fuel derivative contracts Prepaid expenses and other current assets $ 13 $ (3) $ 10 $ 48 $ (10) $ 38 Fuel derivative contracts Other assets $ 121 $ (31) $ 90 (a) $ 62 $ (15) $ 47 (a) Interest rate derivative contracts Other assets $ — $ — $ — (a) $ 2 $ — $ 2 (a) (a) The net amounts of derivative assets and liabilities are reconciled to the individual line item amounts presented in the Consolidated Balance Sheet in Note 16.
Offsetting Liabilities	Offsetting of derivative liabilities (in millions) (i) (ii) (iii) = (i) + (ii) (i) (ii) (iii) = (i) + (ii) December 31, 2020 December 31, 2019 Description Balance Sheet location Gross amounts of recognized liabilities Gross amounts offset in the Balance Sheet Net amounts of liabilities presented in the Balance Sheet Gross amounts of recognized liabilities Gross amounts offset in the Balance Sheet Net amounts of liabilities presented in the Balance Sheet Fuel derivative contracts Prepaid expenses and other current assets $ 3 $ (3) $ — $ 10 $ (10) $ — Fuel derivative contracts Other assets $ 31 $ (31) $ — (a) $ 15 $ (15) $ — (a) Interest rate derivative contracts Accrued liabilities $ — $ — $ — $ 5 $ — $ 5 Interest rate derivative contracts Other noncurrent liabilities $ 6 $ — $ 6 $ 1 $ — $ 1 (a) The net amounts of derivative assets and liabilities are reconciled to the individual line item amounts presented in the Consolidated Balance Sheet in Note 16.
Derivatives in Cash Flow Hedging Relationships	The following tables present the impact of derivative instruments and their location within the Consolidated Statement of Income (Loss) for the year ended December 31, 2020 and 2019: Location and amount recognized in income on cash flow and fair value hedging relationships Year ended December 31, 2020 Year ended December 31, 2019 (in millions) Fuel and oil Other (gains)/losses, net Interest expense Fuel and oil Interest expense Total $ 70 $ 39 $ 6 $ 48 $ 29 Loss on cash flow hedging relationships Commodity contracts: Amount of loss reclassified from AOCI into income 70 39 — 48 — Interest contracts: Amount of loss reclassified from AOCI into income — — 1 — 5 Impact of fair value hedging relationships: Interest contracts: Hedged items — — 11 — 22 Derivatives designated as hedging instruments — — (6) — 2 Derivatives designated and qualified in cash flow hedging relationships Loss recognized in AOCI on derivatives, net of tax Year ended December 31, (in millions) 2020 2019 Fuel derivative contracts $ 80 $ 90 Interest rate derivatives 26 29 Total $ 106 $ 119
Derivatives Not in Cash Flow Hedging Relationships	Derivatives not designated as hedges Loss recognized in income on derivatives Year ended December 31, Location of loss recognized in income on derivatives (in millions) 2020 2019 Fuel derivative contracts $ 1 $ — Other (gains) losses, net Interest rate derivatives 28 — Other (gains) losses, net Total $ 29 $ —
Premiums Paid for Fuel Derivative Contracts	The following table presents the impact of premiums paid for fuel derivative contracts and their location within the Consolidated Statement of Income (Loss) during the period the contract settles: Premium expense recognized in income on derivatives Year ended December 31, Location of premium expense recognized in income on derivatives (in millions) 2020 2019 2018 Fuel derivative contracts designated as hedges $ 64 $ 95 $ 135 Fuel and oil Fuel derivative contracts not designated as hedges $ 34 $ — $ — Other (gains) losses, net
Fair Values of Fuel Derivatives, Amounts Posted as Collateral, and Collateral Posting Threshold Amounts	The following table provides the fair values of fuel derivatives, amounts posted as collateral, and applicable collateral posting threshold amounts as of December 31, 2020, at which such postings are triggered: Counterparty (CP) (in millions) A B C D E F Other (a) Total Fair value of fuel derivatives $ 33 $ 15 $ 33 $ 14 $ 17 $ 11 $ 11 $ 134 Cash collateral held from CP 34 — — — — — — 34 Letters of credit (LC) — — — — — — — — Option to substitute LC for cash N/A N/A (75) to (150) or >(550)(b) (125) to (150) or >(550)(c) (c) N/A If credit rating is investment Cash is provided to CP >(100) >(50) (75) to (150) or >(550)(d) (125) to (150) or >(550)(d) >(40) >(65)(d) Cash is received from CP >0(d) >150(d) >250(d) >(125)(d) >100(d) >70(d) Cash can be pledged to (200) to (600)(e) N/A (150) to (550)(b) (150) to (550)(b) N/A N/A If credit rating is non-investment Cash is provided to CP (0) to (200) or >(600) (f) (0) to (150) or >(550) (0) to (150) or >(550) (f) (f) Cash is received from CP (f) (f) (f) (f) (f) (f) Cash can be pledged to (200) to (600) N/A (150) to (550) (150) to (550) N/A N/A (a) Individual counterparties with fair value of fuel derivatives <$10 million. (b) The Company has the option of providing cash or letters of credit as collateral. (c) The Company has the option to substitute letters of credit for 100 percent of cash collateral requirement. (d) Thresholds may vary based on changes in credit ratings within investment grade. (e) The Company has the option of providing cash as collateral.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following tables present the Company’s assets and liabilities that are measured at fair value on a recurring basis at December 31, 2020, and December 31, 2019: Fair value measurements at reporting date using: Quoted prices in active markets for identical assets Significant other observable inputs Significant unobservable inputs Description December 31, 2020 (Level 1) (Level 2) (Level 3) Assets (in millions) Cash equivalents: Cash equivalents (a) $ 10,663 $ 10,663 $ — $ — Commercial paper 90 — 90 — Certificates of deposit 10 — 10 — Time deposits 300 — 300 — Short-term investments: Treasury bills 1,800 1,800 — — Certificates of deposit 46 — 46 — Time deposits 425 — 425 — Fuel derivatives: Option contracts (b) 134 — — 134 Other available-for-sale securities 259 259 — — Total assets $ 13,727 $ 12,722 $ 871 $ 134 Liabilities Interest rate derivatives (see Note 11) $ (6) $ — $ (6) $ — (a) Cash equivalents are primarily composed of money market investments. (b) In the Consolidated Balance Sheet amounts are presented as an asset. See Note 11. Fair value measurements at reporting date using: Quoted prices in active markets for identical assets Significant other observable inputs Significant unobservable inputs Description December 31, 2019 (Level 1) (Level 2) (Level 3) Assets (in millions) Cash equivalents: Cash equivalents (a) $ 1,999 $ 1,999 $ — $ — Commercial paper 535 — 535 — Certificates of deposit 14 — 14 — Short-term investments: Treasury bills 1,196 1,196 — — Certificates of deposit 268 — 268 — Time deposits 60 — 60 — Interest rate derivatives (see Note 11) 2 — 2 — Fuel derivatives: Option contracts (b) 110 — — 110 Other available-for-sale securities 197 197 — — Total assets $ 4,381 $ 3,392 $ 879 $ 110 Liabilities Interest rate derivatives (see Note 11) $ (6) $ — $ (6) $ — (a) Cash equivalents are primarily composed of money market investments. (b) In the Consolidated Balance Sheet amounts are presented as an asset. See Note 11.
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation	The following tables present the Company’s activity for items measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for 2020 and 2019: Fair value measurements using significant unobservable inputs (Level 3) (in millions) Fuel derivatives Balance at December 31, 2019 $ 110 Total (realized or unrealized) losses for the period Included in earnings (40) (a) Included in other comprehensive loss (65) Purchases 129 (b) Balance at December 31, 2020 $ 134 The amount of total losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held at December 31, 2020 $ (15) (a) The amount of total losses for the period included in other comprehensive loss attributable to the change in unrealized gains or losses relating to assets still held at December 31, 2020 $ (41) (a) Included in Other (gains) losses, net, within the Consolidated Statement of Comprehensive Income (Loss). (b) The purchase of fuel derivatives is recorded gross based on the structure of the derivative instrument and whether a contract with multiple derivatives was purchased as a single instrument or separate instruments. Fair value measurements using significant unobservable inputs (Level 3) (in millions) Fuel derivatives Balance at December 31, 2018 $ 138 Total losses (realized or unrealized) included in other comprehensive income (loss) (112) Purchases 133 (a) Sales (2) (a) Settlements (47) Balance at December 31, 2019 $ 110 (a) The purchase and sale of fuel derivatives are recorded gross based on the structure of the derivative instrument and whether a contract with multiple derivatives was purchased as a single instrument or separate instruments.
Fair Value Valuation Techniques	The following table presents a range and weighted average of the unobservable inputs utilized in the fair value measurements of the Company’s fuel derivatives classified as Level 3 at December 31, 2020: Quantitative information about Level 3 fair value measurements Valuation technique Unobservable input Period (by year) Range Weighted Average (a) Fuel derivatives Option model Implied volatility 2021 29-43% 33 % 2022 25-32% 28 % 2023 23-26% 25 % Beyond 2023 25-26% 25 %
Fair value, by Balance Sheet Grouping	The carrying amounts and estimated fair values of the Company’s short-term and long-term debt (including current maturities), as well as the applicable fair value hierarchy tier, at December 31, 2020, are presented in the table below. The fair values of the Company’s publicly held long-term debt are determined based on inputs that are readily available in public markets or can be derived from information available in publicly quoted markets; therefore, the Company has categorized these agreements as Level 2. Debt under four of the Company’s debt agreements is not publicly held. The Company has determined the estimated fair value of this debt to be Level 3, as certain inputs used to determine the fair value of these agreements are unobservable. The Company utilizes indicative pricing from counterparties and a discounted cash flow method to estimate the fair value of the Level 3 items. (in millions) Carrying value Estimated fair value Fair value level hierarchy 2.75% Notes due 2022 $ 300 $ 311 Level 2 Pass Through Certificates due 2022 - 6.24% 137 140 Level 2 4.75% Notes due 2023 1,250 1,362 Level 2 1.25% Convertible Notes due 2025 1,945 3,359 Level 2 5.25% Notes due 2025 1,550 1,799 Level 2 Term Loan Agreement payable through 2025 - 1.65% 119 119 Level 3 3.00% Notes due 2026 300 324 Level 2 Term Loan Agreement payable through 2026 - 1.34% 159 155 Level 3 3.45% Notes due 2027 300 329 Level 2 5.125% Notes due 2027 2,000 2,383 Level 2 7.375% Debentures due 2027 119 145 Level 2 Term Loan Agreement payable through 2028 - 1.65% 184 183 Level 3 2.625% Notes due 2030 500 515 Level 2 1.000% Payroll Support Program Loan due 2030 976 953 Level 3

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Rollforward of the Amounts Included in AOCI, Net of Taxes	A rollforward of the amounts included in AOCI, net of taxes, is shown below for 2020 and 2019: (in millions) Fuel derivatives Interest rate derivatives Defined benefit plan items Other Deferred tax impact Accumulated other Balance at December 31, 2018 $ (56) $ — $ 58 $ 25 $ (7) $ 20 Changes in fair value (117) (38) (38) 34 37 (122) Reclassification to earnings 48 5 — — (12) 41 Balance at December 31, 2019 $ (125) $ (33) $ 20 $ 59 $ 18 $ (61) Changes in fair value (103) (34) (63) 32 39 (129) Reclassification to earnings 109 1 — — (25) 85 Balance at December 31, 2020 $ (119) $ (66) $ (43) $ 91 $ 32 $ (105)
Reclassification out of Accumulated Other Comprehensive Income	The following table illustrates the significant amounts reclassified out of each component of AOCI for the year ended December 31, 2020: Year ended December 31, 2020 (in millions) Amounts reclassified from AOCI Affected line item in the Consolidated Statement of Comprehensive Income (Loss) AOCI components Unrealized loss on fuel derivative instruments $ 70 Fuel and oil expense 39 Other (gains) losses, net 25 Less: Tax expense $ 84 Net of tax Unrealized loss on interest rate derivative instruments $ 1 Interest expense — Less: Tax expense $ 1 Net of tax Total reclassifications for the period $ 85 Net of tax

Employee Retirement Plans (Tabl

Employee Retirement Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Schedule of Changes in Accumulated Postemployment Benefit Obligations	The following table shows the change in the accumulated postretirement benefit obligation ("APBO") for the years ended December 31, 2020 and 2019: (in millions) 2020 2019 APBO at beginning of period $ 288 $ 232 Service cost 22 17 Interest cost 10 10 Benefits paid (10) (9) Actuarial loss 63 38 Curtailment 53 — Special termination benefits 2 — APBO at end of period $ 428 $ 288
Schedule of Amounts Recognized in Balance Sheet	The following table reconciles the funded status of the plans to the accrued postretirement benefit cost recognized in Other non-current liabilities on the Company’s Consolidated Balance Sheet at December 31, 2020 and 2019. (in millions) 2020 2019 Funded status $ (428) $ (288) Unrecognized net actuarial (gain) loss 40 (24) Unrecognized prior service cost 3 4 Accumulated other comprehensive income (loss) (43) 20 Consolidated Balance Sheet liability $ (428) $ (288)
Schedule of Net Benefit Costs	The consolidated periodic postretirement benefit cost for the years ended December 31, 2020, 2019, and 2018, included the following: (in millions) 2020 2019 2018 Service cost $ 22 $ 17 $ 18 Interest cost 10 10 9 Amortization of prior service cost 1 1 3 Amortization of net gain — (2) — Curtailment 53 — — Special termination benefits 2 — — Net periodic postretirement benefit cost $ 88 $ 26 $ 30
Schedule of Assumptions Used	The following actuarial assumptions were used to account for the Company’s postretirement benefit plans at December 31, 2020, 2019, and 2018: 2020 2019 2018 Weighted-average discount rate 2.45 % 3.30 % 4.35 % Assumed healthcare cost trend rate (a) 6.75 % 7.13 % 7.13 % (a) The assumed healthcare cost trend rate is expected to be 6.50% for 2021, then decline gradually to 4.75% by 2028 and remain level thereafter.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Components of Deferred Tax Assets and Liabilities	The components of deferred tax assets and liabilities at December 31, 2020 and 2019, are as follows: (in millions) 2020 2019 DEFERRED TAX LIABILITIES: Accelerated depreciation $ 2,939 $ 3,096 Prepaid insurance 190 12 Operating lease right-of-use assets 423 293 Other 67 81 Total deferred tax liabilities 3,619 3,482 DEFERRED TAX ASSETS: Accrued employee benefits 491 346 Rapid rewards loyalty liability 632 305 Operating lease liabilities 443 308 Residual travel funds 117 — Construction obligation 72 38 Net operating losses and tax credits 60 (a) 8 Other 170 113 Total deferred tax assets 1,985 1,118 Net deferred tax liability $ 1,634 $ 2,364
Components of the Income Tax Provision	The provision (benefit) for income taxes is composed of the following: (in millions) 2020 2019 2018 CURRENT: Federal (a) $ (273) $ 610 $ 338 State (5) 102 60 Change in federal statutory rate (b) (188) — — Total current (466) 712 398 DEFERRED: Federal (a) (589) (18) 299 State (76) (6) 2 State net operating losses (51) — — Change in federal statutory tax rate (c) — (31) — Total deferred (716) (55) 301 $ (1,182) $ 657 $ 699 (a) The CARES Act allows entities to carry back 2020 losses to prior periods of up to five years, and claim refunds of federal taxes paid, and the Company expects to receive a significant cash tax refund once it completes all the necessary requirements to make the appropriate filings with the IRS. (b) The benefit is representative of the excess refund generated as the result of carrying the 2020 losses back to a period when the federal statutory tax rate was 35 percent as opposed to the current tax rate of 21 percent. (c) The Tax Cuts and Jobs Act was enacted in December 2017, which reduced the U.S. federal corporate tax rate from the previous rate of 35 percent to 21 percent.
Income Tax Provision Reconciliation To Federal Income Tax Statutory Rate	The effective tax rate on Income (loss) before income taxes differed from the federal income tax statutory rate for the following reasons: (in millions) 2020 2019 2018 Tax at statutory U.S. tax rates $ (894) $ 621 $ 664 State income taxes, net of federal benefit (115) 76 49 Change in federal statutory tax rate (188) (a) (31) (b) — Other, net 15 (9) (14) Total income tax provision (benefit) $ (1,182) $ 657 $ 699 (a) The benefit is representative of the excess refund generated as the result of carrying the 2020 losses back to a period when the federal statutory tax rate was 35 percent as opposed to the current tax rate of 21 percent. (b) The Tax Cuts and Jobs Act was enacted in December 2017, which reduced the U.S. federal corporate tax rate from the previous rate of 35 percent to 21 percent.

Supplemental Financial Inform_2

Supplemental Financial Information (Tables)	12 Months Ended
	Dec. 31, 2020
Table Text Block [Abstract]
Accounts and Other Receivables	(in millions) December 31, 2020 December 31, 2019 Trade receivables $ 46 $ 53 Credit card receivables 35 112 Business partners and other suppliers 274 779 Taxes receivable 740 (a) 87 Other 35 55 Accounts and other receivables $ 1,130 $ 1,086
Other Assets	(in millions) December 31, 2020 December 31, 2019 Derivative contracts $ 90 $ 49 Intangible assets, net 295 296 Other 337 232 Other assets $ 722 $ 577
Accounts Payable	(in millions) December 31, 2020 December 31, 2019 Accounts payable trade $ 111 $ 304 Salaries payable 201 231 Taxes payable excluding income taxes 49 227 Aircraft maintenance payable 95 162 Fuel payable 66 129 Dividends payable — 93 Other payable 409 428 Accounts payable $ 931 $ 1,574
Accrued Liabilities	(in millions) December 31, 2020 December 31, 2019 Extended Emergency Time Off $ 393 $ — Voluntary Separation Program 2020 143 — Profitsharing and savings plans 25 695 Vendor prepayment 600 (b) — Vacation pay 436 434 Health 111 120 Workers compensation 161 166 Property and income taxes 84 79 Interest 49 16 Other 257 239 Accrued liabilities $ 2,259 $ 1,749
Other Noncurrent Liabilities	(in millions) December 31, 2020 December 31, 2019 Extended Emergency Time Off $ 57 $ — Voluntary Separation Program 2020 321 — Postretirement obligation 428 288 Other deferred compensation 353 313 Other 88 105 Other noncurrent liabilities $ 1,247 $ 706 (a) This amount includes approximately $470 million associated with a significant cash tax refund expected as a result of the CARES Act allowing entities to carry back 2020 losses to prior periods of up to five years, and claim refunds of federal taxes paid. This amount also includes excise taxes remitted to taxing authorities for which the subsequent flights were canceled by Customers, resulting in amounts due back to the Company. See Note 15 for further information. (b) In fourth quarter 2020, the Company received a $600 million prepayment from Chase for Rapid Rewards points expected to be purchased during 2021, based on cardholder activity on its Visa card associated with its loyalty program. The Company currently expects the majority of this amount to be reclassified to deferred revenue in Air Traffic liability--loyalty during the first half of 2021.

Quarterly Financial Data (Table

Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Data [Abstract]
Schedule of Quarterly Financial Information	Three months ended (in millions except per share amounts) March 31 June 30 Sept. 30 Dec. 31 2020 Operating revenues $ 4,234 $ 1,008 $ 1,793 $ 2,013 Operating income (loss) (110) (1,127) (1,411) (1,169) Income (loss) before income taxes (144) (1,239) (1,542) (1,331) Net income (loss) (94) (915) (1,157) (908) Net income (loss) per share, basic (0.18) (1.63) (1.96) (1.54) Net income (loss) per share, diluted (0.18) (1.63) (1.96) (1.54) March 31 June 30 Sept. 30 Dec. 31 2019 Operating revenues $ 5,149 $ 5,909 $ 5,639 $ 5,729 Operating income 505 968 819 665 Income before income taxes 504 968 819 666 Net income 387 741 659 514 (a) Net income per share, basic 0.70 1.37 1.24 0.98 (a) Net income per share, diluted 0.70 1.37 1.23 0.98 (a)

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2020USD ($)aircraft	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Accounting Policies [Abstract]
Capitalized computer software, net	$ 697,000,000	$ 630,000,000
Computer software depreciation expense	203,000,000	177,000,000	$ 155,000,000
Capitalized computer software, Impairments	0
Advertising costs	156,000,000	212,000,000	215,000,000
Loss on asset impairment	$ (32,000,000)	0	0
Concentration Risk [Line Items]
Percentage Of Employees Represented By Unions Under Collective Bargaining Agreements in Negotiations	55.00%
Number of Aircraft Grounded Under Emergency Order on March 13, 2019 | aircraft	34
Indefinite-Lived Intangible Assets [Line Items]
Goodwill impairment	$ 0
Length of agreements with co-brand, payment, and loyalty partners	10 years
Operating Revenue	$ 9,048,000,000	22,428,000,000	21,965,000,000
Fuel derivatives
Change in Accounting Estimate [Line Items]
Collateral Already Posted, Aggregate Fair Value	34,000,000
Total collateral already posted aggregate fair value	34,000,000	25,000,000
Other Intangible Assets
Indefinite-Lived Intangible Assets [Line Items]
Gross carrying amount of indefinite-lived intangible assets	295,000,000	295,000,000
Other Noncurrent Liabilities | Interest rate derivatives
Change in Accounting Estimate [Line Items]
Collateral Already Posted, Aggregate Fair Value	$ 0	0
Flight equipment
Property, Plant and Equipment [Line Items]
Maximum percentage of cost estimated as residual value (in hundredths)	15.00%
Flight equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment Useful Life	25 years
Ground property and equipment
Property, Plant and Equipment [Line Items]
Minimum percentage of cost estimated residual value (in hundredths)	0.00%
Maximum percentage of cost estimated as residual value (in hundredths)	10.00%
Ground property and equipment | Minimum
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment Useful Life	5 years
Ground property and equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment Useful Life	30 years
Software | Minimum
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment Useful Life	5 years
Software | Maximum
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment Useful Life	15 years
Latin America
Operating Revenue	$ 184,000,000	615,000,000	566,000,000
North America
Operating Revenue	$ 8,900,000,000	$ 21,800,000,000	$ 21,400,000,000
Unionized Employees concentration risk
Concentration Risk [Line Items]
The percentage of Company's employees that are unionized and covered by collective bargaining agreements (in hundredths)	83.00%
B-737-700
Property, Plant and Equipment [Line Items]
Total aircraft retired in 4Q20 | aircraft	20

Worldwide Pandemic (Details)

Worldwide Pandemic (Details) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended				60 Months Ended
	Dec. 31, 2020USD ($)aircraftemployeesshares	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2015	Apr. 19, 2030	Jan. 15, 2021USD ($)shares	Dec. 27, 2020USD ($)	Jun. 30, 2020USD ($)	Apr. 09, 2020$ / shares	Mar. 30, 2020USD ($)
Proceeds from term loan credit facility	$ 3,683	$ 0	$ 0
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	27.80%	22.20%		35.00%
Proceeds from Payroll Support Program Grant	$ 3,400
Cash Raised, Net of Fees	$ 18,900
Class of Warrant or Right, Outstanding | shares	2,700
Proceeds from Payroll Support Program Grant Received in June 2020								$ 652
Voluntary Separation Program 2020 Participants | employees	4,200
Voluntary Separation Program 2020 and Extended Emergency Time Off Total Accrued	$ 914
Extended Emergency Time Off Accrual for Employees who Accepted through 2020	$ 620
Number of Aircraft Grounded Under Emergency Order on March 13, 2019 | aircraft	34
Number of Aircraft in Long-Term Storage | aircraft	92
Proceeds from Payroll Support Program Grant Allocated to Fund Salaries, Wages, and Benefits	$ 2,300
Costs Incurred for Voluntary Separation Program 2020 and Extended ETO	1,400
Goodwill	970	$ 970
Proceeds from Payroll Support Program Extension Grant of Consolidated Appropriations Act that will be Used to Offset Salaries, Wages, and Benefits Expenses in 1Q21	1,700
Unsecured Term Loan to be Issued Through Payroll Support Program Extension of Consolidated Appropriations Act	259
Total Proceeds to be Provided to U.S. Airlines from Payroll Support Program Extension Grant of Consolidated Appropriations Act							$ 15,000
Voluntary Separation Program 2020 and Extended Emergency Time Off Relieved from Accrual for Employees Who Accepted Through December 31, 2020	$ 454
Total Employees who participated in Extended Emergency Time Off During 2020 | employees	11,000
Total Employees who Participated in Extended Emergency Time Off During 2020, Who Were Still on Emergency Time Off at December 31, 2020 | employees	10,421
Impairment of indefinite-lived Intangibles, excluding goodwill	$ 0
Goodwill impairment	0
Loss on asset impairment	(32)	0	$ 0
Goodwill	$ 970	970
B-737-700
Total aircraft retired in 4Q20 | aircraft	20
Option to Convert to Voluntary Separation Program 2020 [Member]
Extended Emergency Time Off Period	12 months
Subsequent Event
Proceeds from Payroll Support Program Extension Grant Received in January 2021						$ 864
Minimum
Extended Emergency Time Off Period	6 months
Maximum
Extended Emergency Time Off Period	18 months
Customer Support and Service [Member]
Voluntary Separation Program 2020 Participants | employees	390
Ground Operations and Provisioning [Member]
Voluntary Separation Program 2020 Participants | employees	1,060
Flight Attendants [Member]
Voluntary Separation Program 2020 Participants | employees	725
Pilots [Member]
Voluntary Separation Program 2020 Participants | employees	630
Pilots [Member] | Maximum
Extended Emergency Time Off Period	5 years
Contract groups [Member]
Voluntary Separation Program 2020 Participants | employees	90
Managerial and Administrative [Member]
Voluntary Separation Program 2020 Participants | employees	1,140
Maintenance [Member]
Voluntary Separation Program 2020 Participants | employees	185
LUV Common Stock Warrants
Class of Warrant or Right, Outstanding | shares	2,700
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares									$ 36.47
Warrants and Rights Outstanding	$ 40
Class of Warrant or Right, Unissued | shares	560
LUV Common Stock Warrants | Subsequent Event
Class of Warrant or Right, Outstanding | shares						495
Common Stock | Subsequent Event
Warrants and Rights Outstanding						$ 9
Use Rights [Member]
Gross carrying amount of indefinite-lived intangible assets	$ 295
CARES Act Unsecured Loan | Unsecured Debt
Interest rate stated in the debt agreement (in hundredths)	1.00%
Unsecured Debt | Forecast | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Spread on variable rate					2.00%
1.0 Payroll Support Program Loan due 2030 | Unsecured Debt
Interest rate stated in the debt agreement (in hundredths)	1.00%
Carrying amount of debt	$ 976	$ 0
1.0 Payroll Support Program Loan due 2031 [Member] | Subsequent Event
Carrying amount of debt						$ 229
Accordian Feature to Amended 364-Day Term Loan Credit Facility [Member] | Amended 364-Day Term Loan Credit Facility
Accordian Feature on Short-term Debt										$ 417

Net Income (Loss) Per Share (De

Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	[1]	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
NUMERATOR:
Net income (loss)	$ (908)	$ (1,157)	$ (915)	$ (94)	$ 514		$ 659	$ 741	$ 387	$ (3,074)	$ 2,300	$ 2,465
DENOMINATOR:
Weighted-average shares outstanding, basic										565	538	573
Dilutive effect of restricted stock units										0	1	1
Adjusted weighted-average shares outstanding, diluted										565	539	574
NET INCOME (LOSS) PER SHARE:
NET INCOME (LOSS) PER SHARE, BASIC	$ (1.54)	$ (1.96)	$ (1.63)	$ (0.18)	$ 0.98		$ 1.24	$ 1.37	$ 0.70	$ (5.44)	$ 4.28	$ 4.30
NET INCOME (LOSS) PER SHARE, DILUTED	$ (1.54)	$ (1.96)	$ (1.63)	$ (0.18)	$ 0.98		$ 1.23	$ 1.37	$ 0.70	$ (5.44)	$ 4.27	$ 4.29
[1]	In addition to the ongoing impact of the Boeing 737 MAX aircraft ("MAX") grounding that impacted all four quarters of 2019, fourth quarter 2019 also included the impact of the pre-tax $124 million discretionary, special profitsharing award accrual authorized by the Company's Board of Directors during fourth quarter 2019 for compensation received from Boeing related to the Company's estimated 2019 financial damages related to the grounding of the Boeing 737 MAX. See Note 17 to the Consolidated Financial Statements for further information on the MAX groundings. The impact of this accrual resulted in a decrease to Net income of approximately $97 million and reduced Basic and Diluted net income per share by approximately $.18 for the fourth quarter 2019.

Commitments and Contingengies -

Commitments and Contingengies - Long-term Purchase Commitments (Details) $ in Millions	12 Months Ended		15 Months Ended
	Dec. 31, 2021aircraft	Dec. 31, 2020USD ($)aircraft	Dec. 31, 2021aircraft
Long-term Purchase Commitment
Number of Aircraft Grounded Under Emergency Order on March 13, 2019		34
Property, Plant and Equipment, Total Number of Aircraft Expected to be Leased in 4Q20 and 2021		16
Total Capital Commitments Shifting into Future Periods, Associated with Contractual Obligations that Did Not Take Place in 2019 or 2020 | $		$ 2,100
Capital Commitments from 2019 Shifting Into Future Periods, Associated with Contractual Obligations that Did Not Take Place in 2019 or 2020 | $		743
Capital Commitments from 2020 Shifting into Future Periods, Associated with Contractual Obligations that Did Not Take Place in 2019 or 2020 | $		1,300
Aircraft
Long-term Purchase Commitment
Committed expenditures, 2021 | $		1,700
Committed expenditures, 2022 | $		1,200
Committed expenditures, 2023 | $		1,600
Committed expenditures, 2024 | $		1,900
Committed expenditures, 2025 | $		$ 1,500
B-737-8 Max
Long-term Purchase Commitment
Property, Plant and Equipment, Maximum Number of Purchased Aircraft Expected to be Delivered through December 31, 2021, based on the Memorandum of Understanding Reached in December 2020		19
737 MAX 8
Long-term Purchase Commitment
Long-term Purchase Commitment, Minimum Quantity Required		219
Options - 737MAX (in units)		115
737 MAX 7
Long-term Purchase Commitment
Long-term Purchase Commitment, Minimum Quantity Required		30
737 MAX 8
Long-term Purchase Commitment
Property, Plant and Equipment, Number of Aircraft Leased		7
737 MAX 8 | Subsequent Event
Long-term Purchase Commitment
Property, Plant and Equipment, Number of Aircraft Expected to be Leased in 2021	9
Property, Plant and Equipment, Total Number of Aircraft Expected to be Delivered in 4Q20 and 2021			35

Commitments and Contingencies -

Commitments and Contingencies - Airport Projects (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Airport Project
ACFO	$ 309	$ 164
Depreciation and amortization	1,255	1,219	$ 1,201
Construction obligation	309	164
LosAngelesWorldAirportTerminal1.5 [Member]
Airport Project
Expected total airport modernization project cost	464
Contractual Obligation	318
DAL [Member]
Airport Project
Municipal Bonds Principal Remaining	399
Net Present Value of Principal Remaining	$ 433	$ 444

Revenue - Passenger Revenue Bre

Revenue - Passenger Revenue Breakout (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue
Operating Revenue	$ 9,048	$ 22,428	$ 21,965
Passenger Revenue Non Loyalty
Disaggregation of Revenue
Operating Revenue	6,303	17,578	17,506
Passenger Loyalty Air Transportation
Disaggregation of Revenue
Operating Revenue	1,003	2,487	2,307
Passenger Ancillary Sold Separately
Disaggregation of Revenue
Operating Revenue	359	711	642
Passenger
Disaggregation of Revenue
Operating Revenue	$ 7,665	$ 20,776	$ 20,455

Revenue - Air Traffic Liability

Revenue - Air Traffic Liability Breakout (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
ATL - PAX Revenue and Ancillary PAX Services	$ 2,686	$ 2,125
ATL - Loyalty Program	4,447	3,385
Air Traffic Liability Total	$ 7,133	$ 5,510	$ 5,070

Revenue - Air Traffic Liabili_2

Revenue - Air Traffic Liability - Loyalty Program Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Movement in Deferred Revenue
Air traffic liability - loyalty program - beginning balance	$ 3,385	$ 3,011
Amounts deferred associated with points awarded	1,958	2,941
Revenue recognized from points redeemed - Passenger	(1,003)	(2,487)
Revenue recognized from points redeemed - Other	(60)	(80)
Unused funds converted to loyalty points	167	0
Air traffic liability - loyalty program - ending balance	$ 4,447	$ 3,385

Revenue - Air Traffic Liabili_3

Revenue - Air Traffic Liability Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Air Traffic Liability Rollforward [Abstract]
ATL, beginning balance	$ 5,510	$ 5,070
Current Period Sales	9,348	21,296
Revenue amounts in beginning balance	(2,317)	(3,816)
Revenue from Current Period Sales	(5,408)	(17,040)
ATL, ending balance	$ 7,133	$ 5,510

Revenue - Additional Informatio

Revenue - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred Revenue Arrangement
Operating Revenue	$ 9,048	$ 22,428	$ 21,965
Residual Travel Funds	28.00%	2.00%
Contract with Customer Liability - Customer Travel Funds	$ 2,100
Contract with Customer, Liability, Current - Customer Travel Funds Expiration Date as of December 31, 2020	Sep. 7, 2022
Chase And Other Partner Agreements
Deferred Revenue Arrangement
Operating Revenue	$ 1,100	$ 1,300	$ 1,100

FINANCING ACTIVITIES (Details)

FINANCING ACTIVITIES (Details) $ / shares in Units, shares in Millions	May 01, 2020USD ($)$ / sharesshares	Dec. 31, 2020USD ($)aircraftMortgages$ / shares	Dec. 31, 2020USD ($)aircraftMortgages$ / shares	Dec. 31, 2019USD ($)$ / shares	Dec. 31, 2018USD ($)	Jul. 31, 2020USD ($)	Jun. 08, 2020USD ($)	May 04, 2020USD ($)	Apr. 24, 2020USD ($)	Apr. 09, 2020$ / shares	Apr. 01, 2020USD ($)	Mar. 30, 2020USD ($)
Debt Instrument [Line Items]
Required Minimum Liquidity Level at All Times After March 31, 2021		$ 1,500,000,000	$ 1,500,000,000
Shares Issued, Price Per Share | $ / shares	$ 28.50
Stock Issued During Period, Shares, New Issues | shares	80.5
Common stock, par value (in dollars per share) | $ / shares	$ 1	$ 1	$ 1	$ 1
Gain on sale-leaseback transactions			$ (222,000,000)	$ 0	$ 0
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt			(392,000,000)
Proceeds from issuance of long-term debt			5,622,000,000	0	0
Issuance of common stock			2,294,000,000	0	0
Proceeds from sale-leaseback transactions			815,000,000	0	$ 0
Amortization of Debt Discount (Premium)			48,000,000
Amortization of Debt Issuance Costs			5,000,000
Total lease obligations		$ 542,000,000	542,000,000	627,000,000
Debt and Lease Obligation		10,381,000,000	10,381,000,000	2,678,000,000
Less current maturities		220,000,000	220,000,000	819,000,000
Less debt discount and issuance costs		50,000,000	50,000,000	13,000,000
Long-term debt less current maturities		10,111,000,000	10,111,000,000	1,846,000,000
Letters of Credit Outstanding, Amount		138,000,000	138,000,000
Net book value of assets pledged as collateral for the Company's secured borrowings, primarily aircraft and engines		2,100,000,000	2,100,000,000
Aggregate annual principal maturities of debt and finance leases (not including amounts associated with interest on finance leases) - 2021		220,000,000	220,000,000
Aggregate annual principal maturities of debt and finance leases (not including amounts associated with interest on finance leases) - 2022		524,000,000	524,000,000
Aggregate annual principal maturities of debt and finance leases (not including amounts associated with interest on finance leases) - 2023		1,400,000,000	1,400,000,000
Aggregate annual principal maturities of debt and finance leases (not including amounts associated with interest on finance leases) - 2024		152,000,000	152,000,000
Aggregate annual principal maturities of debt and finance leases (not including amounts associated with interest on finance leases) - 2025		4,000,000,000	4,000,000,000
Aggregate annual principal maturities of debt and finance leases (not including amounts associated with interest on finance leases) - Thereafter		$ 4,400,000,000	$ 4,400,000,000
LUV Common Stock Warrants
Debt Instrument [Line Items]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares										$ 36.47
B-737-800
Debt Instrument [Line Items]
Sale Leaseback Transaction, Description of Asset(s)			ten
Gain on sale-leaseback transactions			$ 153,000,000
Sale Leaseback Transaction, Lease Terms			ten years
Proceeds from sale-leaseback transactions			$ 405,000,000
B-737-8 Max
Debt Instrument [Line Items]
Sale Leaseback Transaction, Description of Asset(s)			ten
Gain on sale-leaseback transactions			$ 69,000,000
Sale Leaseback Transaction, Lease Terms			13 years
Proceeds from sale-leaseback transactions			$ 410,000,000
Amended 364-Day Term Loan Credit Facility
Debt Instrument [Line Items]
Face amount of debt											$ 2,300,000,000
1.250 Convertible Senior Notes due 2025
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Price | $ / shares		$ 38.48	$ 38.48
Debt Instrument, Convertible, Conversion Ratio		25.9909
Debt Instrument, Redemption Price, Percentage		100.00%
Convertible Debt Conversion Terms Percentage of Sales Price Exceeding Conversion Price			130.00%
Convertible Debt Conversion Terms Measurement Period Trading Price Threshold Percentage			98.00%
Interest rate stated in the debt agreement (in hundredths)	1.25%
4.750 Unsecured Notes due 2023
Debt Instrument [Line Items]
Face amount of debt		$ 1,250,000,000	$ 1,250,000,000				$ 500,000,000	$ 750,000,000
Interest rate stated in the debt agreement (in hundredths)								4.75%
5.250 Unsecured Notes due 2025
Debt Instrument [Line Items]
Face amount of debt		$ 1,550,000,000	$ 1,550,000,000					$ 1,250,000,000
5.125 Unsecured Notes due 2027 [Member]
Debt Instrument [Line Items]
Face amount of debt							$ 1,300,000,000
Secured Debt by Six Aircraft [Member]
Debt Instrument [Line Items]
Aircraft Subject to Secure Debt Transactions | aircraft		6	6
Face amount of debt		$ 197,000,000	$ 197,000,000
Debt Instrument, Face Amount, Net of Fees		190,000,000	190,000,000
364-Day Term Loan Credit Facility
Debt Instrument [Line Items]
Face amount of debt		$ 1,000,000,000	$ 1,000,000,000
Secured Debt by Four Aircraft [Member]
Debt Instrument [Line Items]
Aircraft Subject to Secure Debt Transactions | aircraft		4	4
Face amount of debt		$ 125,000,000	$ 125,000,000
Debt Instrument Net of fees		$ 121,000,000	$ 121,000,000
Secured Debt by Four Aircraft [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		1.40%	1.40%
2.65% Notes due 2020
Debt Instrument [Line Items]
Face amount of debt		$ 500,000,000	$ 500,000,000
Interest rate stated in the debt agreement (in hundredths)		2.65%	2.65%
Unsecured Senior Notes Due 2022 - 2.75%
Debt Instrument [Line Items]
Face amount of debt		$ 300,000,000	$ 300,000,000
Interest rate stated in the debt agreement (in hundredths)		2.75%	2.75%
Total Pass Through Certificates [Member]
Debt Instrument [Line Items]
Face amount of debt		$ 500,000,000	$ 500,000,000
Number of mortgages on secured aircraft | Mortgages		16	16
Total Pass Through Certificates [Member] | Interest rate derivatives | Cash Flow Hedging
Debt Instrument [Line Items]
Notional amount		$ 20,000,000	$ 20,000,000
Notional amount		20,000,000	20,000,000
Unsecured Senior Notes Due 2026 - 3.00%
Debt Instrument [Line Items]
Face amount of debt		$ 300,000,000	$ 300,000,000
Interest rate stated in the debt agreement (in hundredths)		3.00%	3.00%
Term Loan Agreement payable through 2026 - 1.34%
Debt Instrument [Line Items]
Number of mortgages on secured aircraft | Mortgages		7	7
Interest rate stated in the debt agreement (in hundredths)		1.34%	1.34%
Term Loan Agreement payable through 2026 - 1.34% | Maximum
Debt Instrument [Line Items]
Face amount of debt		$ 215,000,000	$ 215,000,000
Term Loan Agreement payable through 2026 - 1.34% | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Spread on variable rate			1.10%
Unsecured Senior Notes Due 2027 - 3.45%
Debt Instrument [Line Items]
Face amount of debt		$ 300,000,000	$ 300,000,000
Interest rate stated in the debt agreement (in hundredths)		3.45%	3.45%
Unsecured Senior Notes Due 2027 - 3.45% | Treasury Rate
Debt Instrument [Line Items]
Spread on variable rate			20.00%
7.375% Debentures due 2027
Debt Instrument [Line Items]
Face amount of debt		$ 100,000,000	$ 100,000,000
Interest rate stated in the debt agreement (in hundredths)		7.375%	7.375%
Term Loan Agreement payable through May 2020 - 5.223%
Debt Instrument [Line Items]
Secured Debt		$ 0	$ 0	$ 134,000,000
Face amount of debt		$ 600,000,000	$ 600,000,000
Number of mortgages on secured aircraft | Mortgages		21	21
Interest rate stated in the debt agreement (in hundredths)		5.223%	5.223%	5.223%
Term Loan Agreement payable through May 2020 - 5.223% | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Spread on variable rate			0.95%
Pass Through Certificates Series A
Debt Instrument [Line Items]
Face amount of debt		$ 412,000,000	$ 412,000,000
Interest rate stated in the debt agreement (in hundredths)		6.15%	6.15%
Pass Through Certificates Series B
Debt Instrument [Line Items]
Face amount of debt		$ 88,000,000	$ 88,000,000
Interest rate stated in the debt agreement (in hundredths)		6.65%	6.65%
737 Aircraft Notes payable through 2020 | AirTran Airways
Debt Instrument [Line Items]
Secured Debt		$ 0	$ 0	$ 20,000,000
1.25% convertible notes (a) | 1.250 Convertible Senior Notes due 2025
Debt Instrument [Line Items]
Debt Instrument Underwriters Option to Purchase	$ 300,000,000
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt			$ (11,000,000)
Debt Instrument, Interest Rate, Effective Percentage		5.20%	5.20%
Face amount of debt	$ 2,300,000,000	$ 1,900,000,000	$ 1,900,000,000
Debt Instrument, Convertible, Carrying Amount of Equity Component		403,000,000	403,000,000
Unamortized Debt Issuance Expense		62,000,000	62,000,000
Interest rate stated in the debt agreement (in hundredths)	1.25%
Carrying amount of debt		$ 1,945,000,000	$ 1,945,000,000	0
Unsecured Debt | 2.625% Notes due 2030
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		2.625%	2.625%
Carrying amount of debt		$ 500,000,000	$ 500,000,000	0
Unsecured Debt | 1.250 Convertible Senior Notes due 2025
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		1.25%	1.25%
Unsecured Debt | 4.750 Unsecured Notes due 2023
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		4.75%	4.75%
Carrying amount of debt		$ 1,250,000,000	$ 1,250,000,000	0
Unsecured Debt | 5.250 Unsecured Notes due 2025
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		5.25%	5.25%
Carrying amount of debt		$ 1,550,000,000	$ 1,550,000,000	0		$ 300,000,000
Unsecured Debt | 5.125 Notes due 2027
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		5.125%	5.125%
Carrying amount of debt		$ 2,000,000,000	$ 2,000,000,000	0		700,000,000
Unsecured Debt | 2.65% Notes due 2020
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		2.65%	2.65%
Carrying amount of debt		$ 0	$ 0	500,000,000
Unsecured Debt | Unsecured Senior Notes Due 2022 - 2.75%
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		2.75%	2.75%
Carrying amount of debt		$ 300,000,000	$ 300,000,000	300,000,000
Unsecured Debt | Unsecured Senior Notes Due 2026 - 3.00%
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		3.00%	3.00%
Carrying amount of debt		$ 300,000,000	$ 300,000,000	300,000,000
Unsecured Debt | Unsecured Senior Notes Due 2027 - 3.45%
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		3.45%	3.45%
Unsecured Debt | 7.375% Debentures due 2027
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		7.375%	7.375%
Carrying amount of debt		$ 119,000,000	$ 119,000,000	122,000,000
Unsecured Debt | 1.0 Payroll Support Program Loan due 2030
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		1.00%	1.00%
Carrying amount of debt		$ 976,000,000	$ 976,000,000	0
Unsecured Debt | 3.45 Unsecured Senior Notes due 2027 [Member]
Debt Instrument [Line Items]
Carrying amount of debt		$ 300,000,000	$ 300,000,000	300,000,000
Unsecured Debt | Total 5.125 Notes due 2027 [Member]
Debt Instrument [Line Items]
Carrying amount of debt						$ 2,000,000,000
Enhanced Equipment Trust Certificate | Total Pass Through Certificates [Member]
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		6.24%	6.24%
Carrying amount of debt		$ 137,000,000	$ 137,000,000	197,000,000
Notes Payable to Banks | Term Loan Agreement Due 2025 [Member]
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		1.65%	1.65%
Carrying amount of debt		$ 119,000,000	$ 119,000,000	0
Notes Payable to Banks | Term Loan Agreement payable through 2026 - 1.34%
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		1.34%	1.34%
Carrying amount of debt		$ 159,000,000	$ 159,000,000	178,000,000
Notes Payable to Banks | Term Loan Agreement Due 2028 [Member]
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		1.65%	1.65%
Notes Payable to Banks | 1.65 Term Loan Agreement Payable through 2028 [Member]
Debt Instrument [Line Items]
Carrying amount of debt		$ 184,000,000	$ 184,000,000	$ 0
Revolving Credit Facility
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 1,500,000,000	$ 1,500,000,000
Amended 364-Day Term Loan Credit Facility
Debt Instrument [Line Items]
Debt Instrument, Collateral			73
Amended 364-Day Term Loan Credit Facility | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		1.00%	1.00%
Amended 364-Day Term Loan Credit Facility | London Interbank Offered Rate (LIBOR) [Member] | Minimum
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		1.00%	1.00%
Amended 364-Day Term Loan Credit Facility | New York Fed Bank Rate [Member]
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		0.50%	0.50%
Amended 364-Day Term Loan Credit Facility | Base Rate [Member] | Minimum
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		1.00%	1.00%
Accordian Feature to Amended 364-Day Term Loan Credit Facility [Member] | Amended 364-Day Term Loan Credit Facility
Debt Instrument [Line Items]
Accordian Feature on Short-term Debt												$ 417,000,000
Face amount of debt									$ 350,000,000
Secured Debt by Six Aircraft [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)		1.40%	1.40%
Existing Revolving Credit Facility [Member] | Revolving Credit Facility
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity		$ 1,000,000,000	$ 1,000,000,000
Revolving Credit Facility, Fair Value Amount Outstanding		0	0
Existing Revolving Credit Facility [Member] | 364-Day Term Loan Credit Facility
Debt Instrument [Line Items]
Face amount of debt		$ 1,000,000,000	$ 1,000,000,000

Leases (Details)

Leases (Details)	12 Months Ended
	Dec. 31, 2020USD ($)aircraft	Dec. 31, 2019USD ($)aircraft	Dec. 31, 2018USD ($)
Sublease Income	$ 78,000,000	$ 97,000,000
Sublease income - 2021	41,000,000
Sublease income - 2022	17,000,000
Sublease income - 2023	7,000,000
Sublease income - 2024	1,000,000
Unrecorded Unconditional Purchase Obligation	$ 291,000,000
Lessee, Operating Lease, Lease Not yet Commenced, Description | aircraft	9
Proceeds from sale-leaseback transactions	$ 815,000,000	0	$ 0
Gain on sale-leaseback transactions	$ (222,000,000)	$ 0	$ 0
B-717-200
Property Subject to or Available for Operating Lease, Number of Units | aircraft	45
Finance Leases, Net Investment in Sales Type Leases, Contingent Payments on Leased Property	$ 0
Finance Leases, Net Investment in Sales Type Leases, Unguaranteed Residual Values of Leased Property	$ 0
Finance Leased Assets, Number of Units | aircraft	2
Property Subject To Or Available For Lease, Number Of Units, Total | aircraft	88
B-737-800
Sale Leaseback Transaction, Description of Asset(s)	ten
Proceeds from sale-leaseback transactions	$ 405,000,000
Sale Leaseback Transaction, Lease Terms	ten years
Gain on sale-leaseback transactions	$ 153,000,000
B-737-8 Max
Sale Leaseback Transaction, Description of Asset(s)	ten
Proceeds from sale-leaseback transactions	$ 410,000,000
Sale Leaseback Transaction, Lease Terms	13 years
Gain on sale-leaseback transactions	$ 69,000,000
Minimum | B-717-200
Sublease Terms	1 month
Minimum | 737 MAX 8
Lessee, Renewal Term	8 years
Minimum | Aircraft
Lessee, Renewal Term	3 months
Lessee Operating and Finance Lease Term of Contract	1 month
Minimum | Airport-Related
Lessee, Renewal Term	6 months
Lessee Operating Lease Terms of Contract	1 month
Minimum | Other Property
Lessee, Renewal Term	6 months
Lessee Operating and Finance Lease Term of Contract	3 months
Maximum | B-717-200
Sublease Terms	4 years
Maximum | 737 MAX 8
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	9 years
Maximum | Aircraft
Lessee, Renewal Term	6 years
Lessee Operating and Finance Lease Term of Contract	13 years
Maximum | Airport-Related
Lessee, Renewal Term	10 years
Lessee Operating Lease Terms of Contract	40 years
Maximum | Other Property
Lessee, Renewal Term	5 years
Lessee Operating and Finance Lease Term of Contract	6 years
Assets Sold to Third Party | B-717-200
Owned Assets, Number of Units | aircraft		10
Lease Expired | B-717-200
Property Subject To Or Available For Lease, Number Of Units, Total | aircraft	20	8

Leases Lease-Related Assets and

Leases Lease-Related Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Operating lease right-of-use assets	$ 1,892	$ 1,349
Finance lease right-of-use assets	667	779
Finance Lease, Right of Use Asset, Accumulated Depreciation	567	455
Total lease assets	2,559	2,128
Current operating lease liabilities	306	353
Finance lease, current maturities of long-term debt	83	85
Noncurrent operating lease liabilities	1,562	978
Finance lease, long-term debt less current maturities	459	542
Total lease liabilities	2,410	$ 1,958
Operating Lease
Current operating lease liabilities	306
Noncurrent operating lease liabilities	1,562
Finance Lease
Finance lease, current maturities of long-term debt	83
Finance lease, long-term debt less current maturities	$ 459

Leases Components of Lease Cost

Leases Components of Lease Cost (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Short-term Lease, Cost		$ 1	$ 4
Variable Lease, Cost		1,260	1,377
Sublease Income		78	97
Finance Lease, Right-of-Use Asset, Amortization		113	116
Finance Lease, Interest Expense		22	26
Lease, Cost		135	142
Other Property
Operating Lease, Cost		89	89
Type of Aircraft [Domain]
Operating Lease, Cost	[1]	$ 216	$ 182
[1]	Net of sublease income of $78 million and $97 million for the years ended December 31, 2020 and 2019.

Leases Supplemental Cash Flow I

Leases Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Payments for Operating Activities [Abstract]
Operating Lease, Payments	$ 398	$ 379
Finance Lease, Interest Payment on Liability	22	26
Finance Lease, Principal Payments	85	85
Right-of-use assets acquired under operating leases	915	230
Right-of-use assets acquired under finance leases	$ 0	$ 1

Leases Maturity of Lease Liabil

Leases Maturity of Lease Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Total lease obligations	$ 542	$ 627
Current operating lease liabilities	(306)	(353)
Finance lease, current maturities of long-term debt	(83)	(85)
Noncurrent operating lease liabilities	1,562	978
Finance lease, long-term debt less current maturities	459	$ 542
Operating Lease
2021	371
2022	253
2023	219
2024	193
2025	156
Thereafter	1,156
Total lease payments	2,348
Less imputed interest	(480)
Total lease obligations	1,868
Current operating lease liabilities	(306)
Noncurrent operating lease liabilities	1,562
Finance Lease
2021	102
2022	98
2023	94
2024	90
2025	74
Thereafter	156
Total lease payments	614
Less imputed interest	(72)
Total lease obligations	542
Finance lease, current maturities of long-term debt	(83)
Finance lease, long-term debt less current maturities	$ 459

Leases Other Information (Detai

Leases Other Information (Details)	Dec. 31, 2020		Dec. 31, 2019
Leases - Other Information [Abstract]
Operating Lease, Weighted Average Remaining Lease Term	10 years		9 years
Finance Lease, Weighted Average Remaining Lease Term	7 years		8 years
Operating Lease, Weighted Average Discount Rate, Percent	3.80%	[1]	3.70%
Finance Lease, Weighted Average Discount Rate, Percent	3.80%		3.80%
[1]	Upon adoption of the New Lease Standard, the incremental borrowing rate used for existing leases was established as of January 1, 2019.

Common Stock (Details)

Common Stock (Details) - $ / shares shares in Millions	May 01, 2020	Dec. 31, 2020	Dec. 31, 2019
Equity [Abstract]
Stock Issued During Period, Shares, New Issues	80.5
Common stock, par value (in dollars per share)	$ 1	$ 1	$ 1
Shares Issued, Price Per Share	$ 28.50
Class of Warrant or Right, Outstanding		2.7
Common stock reserved for issuance pursuant to Employee stock benefit plans (in shares)		60
Common stock reserved for issuance and not granted pursuant to Employee stock benefit plans (in shares)		25
Stock Issued During Period Shares New Issues - Underwriters Option	10.5

Stock Plans (Details)

Stock Plans (Details) - USD ($)		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Employee service share based compensation aggregate disclosures [Abstract]
Share based compensation cost		$ 17,000,000		$ 55,000,000		$ 46,000,000
Total unrecognized compensation cost related to share-based compensation arrangements		$ 29,000,000
Weighted average period of time over which unrecognized compensation cost is to be recognized		1 year 9 months 18 days
The remaining number of RSU's or stock options that may be issued (in shares)		25,000,000
Additional disclosures for all plans for the period [Abstract]
The remaining balance of shares originally authorized for issue under the employee stock purchase plan (in shares)		6,000,000
The percentage of market value at which shares may be issued to participating employees (in hundredths)		90.00%
The discount percentage off the market value for the employee stock purchase plan (in hundredths)		10.00%
Employee stock purchase plan [Abstract]
The remaining balance of shares originally authorized for issue under the employee stock purchase plan (in shares)		6,000,000
The percentage of market value at which shares may be issued to participating employees (in hundredths)		90.00%
The number of shares issued to participants under the plan during the period		1,386,000		821,000		661,000
The weighted average fair value of each purchase right under the employee stock purchase plan (in dollars per share)		$ 34.39		$ 47.60		$ 50.73
The discount percentage off the market value for the employee stock purchase plan (in hundredths)		10.00%
The aggregate cost of the discount from the market value on shares issued to employees at the end of each monthly purchase period	[1]	$ 3.82		$ 5.29		$ 5.64
Stock Compensation Plan - Board of Directors
Employee service share based compensation aggregate disclosures [Abstract]
Non-option equity instruments granted (in shares)		54,000		31,000		28,000
Weighted average price of non-option equity instruments granted		$ 29.60		$ 52.01		$ 53.01
Restricted stock units
Employee service share based compensation aggregate disclosures [Abstract]
Vesting periods for plans		3 years
The remaining number of RSU's or stock options that may be issued (in shares)		19,000,000
Units (000)
Outstanding RSU's - beginning balance (in shares)		1,545,000		1,342,000		1,294,000
Granted (in shares)		1,235,000	[2]	994,000	[3]	782,000	[4]
Vested (in shares)		(715,000)		(744,000)		(670,000)
Surrendered (in shares)		(103,000)		(47,000)		(64,000)
Outstanding RSU's - ending balance (in shares)		1,962,000		1,545,000		1,342,000
Wtd. Average Fair Value (per share)
Weighted average grant date fair value RSU's - beginning balance (in dollars per share)		$ 57.65		$ 52.56		$ 45.32
Weighted average grant date fair value RSU's - granted (in dollars per share)		56.89		57.49		60.80
Weighted average grant date fair value RSU's - vested (in dollars per share)		54.70		42.42		45.11
Weighted average grant date fair value RSU's - surrendered (in dollars per share)		58.04		57.72		47.05
Weighted average grant date fair value RSU's - period end (in dollars per share)		$ 57.81		$ 57.65		$ 52.56
Performance Shares
Units (000)
Granted (in shares)		519,000		387,000		308,000
Minimum | Performance Shares
Employee service share based compensation aggregate disclosures [Abstract]
Percentage of PBRSUs to be granted		0.00%
Maximum | Performance Shares
Employee service share based compensation aggregate disclosures [Abstract]
Percentage of PBRSUs to be granted		200.00%
[1]	The weighted-average fair value of each purchase right under the ESPP granted is equal to a ten percent discount from the market value of the Common Stock at the end of each monthly purchase period.
[2]	Includes 519 thousand PBRSUs
[3]	Includes 387 thousand PBRSUs
[4]	Includes 308 thousand PBRSUs

Financial Derivative Instrume_3

Financial Derivative Instruments Narrative (Details) $ in Millions		12 Months Ended
		Dec. 31, 2020USD ($)aircraftAgreements	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Derivative [Line Items]
Percentage of actual consumption hedged		77.00%
Current Unrealized Net Loss in OCI		$ 54
Maximum sum of derivatives of counterparty to be included in other (less than $10 million)		$ 10
Cash collateral provided as a percentage of derivative contract value (in hundredths)		100.00%
Derivative Asset, Fair Value, Gross Asset		$ 134	$ 112
Derivative Liability, Fair Value, Gross Liability		6	6
Payments of terminated interest rate derivative instruments		$ 59	$ 0	$ 0
Interest Rate Swap Derivative, Aircraft Leases Received in December 2020 | aircraft		3
Term Loan Agreement Due 2020 [Member]
Derivative [Line Items]
Interest rate stated in the debt agreement (in hundredths)		5.223%	5.223%
Unsecured Senior Notes Due 2027
Derivative [Line Items]
Interest rate stated in the debt agreement (in hundredths)		3.45%
2.65% Notes due 2020
Derivative [Line Items]
Interest rate stated in the debt agreement (in hundredths)		2.65%
Unsecured Debt | Unsecured Senior Notes Due 2027
Derivative [Line Items]
Interest rate stated in the debt agreement (in hundredths)		3.45%
Unsecured Debt | 2.65% Notes due 2020
Derivative [Line Items]
Interest rate stated in the debt agreement (in hundredths)		2.65%
Fuel derivatives
Derivative [Line Items]
Collateral Already Posted, Aggregate Fair Value		$ 34
Total collateral already posted aggregate fair value		34	$ 25
Interest rate derivatives
Derivative [Line Items]
Discontinuation of Interest Rate Cash Flow Hedge Balance in AOCI		$ 32
Interest Rate Swaption [Member]
Derivative [Line Items]
Interest Rate Swap Derivative, Aircraft Leases		12	12
Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		$ 130	$ 112
Derivative Liability, Fair Value, Gross Liability		6	6
Not Designated as Hedging Instrument | Fuel derivatives
Derivative [Line Items]
Loss on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring		39
Not Designated as Hedging Instrument | Interest rate derivatives
Derivative [Line Items]
Discontinuation of Interest Rate Cash Flow Hedge Balance in AOCI		31
(Gain) Loss on Interest Rate Derivative Instruments Not Designated as Hedging Instruments		28
Other Noncurrent Liabilities | Interest rate derivatives
Derivative [Line Items]
Collateral Already Posted, Aggregate Fair Value		0	0
Derivative Liability, Fair Value, Gross Liability		6
Other Noncurrent Liabilities | Designated as Hedging Instrument | Interest rate derivatives
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	[1]	6	1
Other Assets | Designated as Hedging Instrument | Fuel derivatives
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	121	62
Other Assets | Designated as Hedging Instrument | Interest rate derivatives
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	$ 0	$ 2
[1]	Represents the position of each trade before consideration of offsetting positions with each counterparty and does not include the impact of cash collateral deposits provided to or received from counterparties. See discussion of credit risk and collateral following in this Note.

Financial Derivative Instrume_4

Financial Derivative Instruments - Fuel Hedging (Details) gal in Millions	Dec. 31, 2020gal	[1]
2021
Volume of Fuel Hedging
Fuel Hedged (in gallons)	1,283
2022
Volume of Fuel Hedging
Fuel Hedged (in gallons)	1,220
2023
Volume of Fuel Hedging
Fuel Hedged (in gallons)	643
Beyond 2023
Volume of Fuel Hedging
Fuel Hedged (in gallons)	101
[1]	Due to the types of derivatives utilized by the Company and different price levels of those contracts, these volumes represent the maximum economic hedge in place and may vary significantly as market prices and the Company's flight schedule fluctuate.

Financial Derivative Instrume_5

Financial Derivative Instruments - Fair Values by Balance Sheet Location (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value
Derivative Asset, Fair Value, Gross Asset		$ 134	$ 112
Derivative Liability, Fair Value, Gross Liability		6	6
Designated as Hedging Instrument
Derivatives, Fair Value
Derivative Asset, Fair Value, Gross Asset		130	112
Derivative Liability, Fair Value, Gross Liability		6	6
Fuel derivatives | Designated as Hedging Instrument | Prepaid expenses and other current assets
Derivatives, Fair Value
Derivative Asset, Fair Value, Gross Asset	[1]	9	48
Derivative Asset, Fair Value, Gross Liability	[1]	0	0
Fuel derivatives | Designated as Hedging Instrument | Other Assets
Derivatives, Fair Value
Derivative Asset, Fair Value, Gross Asset	[1]	121	62
Derivative Asset, Fair Value, Gross Liability	[1]	0	0
Fuel derivatives | Not Designated as Hedging Instrument | Prepaid expenses and other current assets
Derivatives, Fair Value
Derivative Asset, Fair Value, Gross Asset	[1]	4	0
Derivative Asset, Fair Value, Gross Liability	[1]	0	0
Interest rate derivatives | Other Noncurrent Liabilities
Derivatives, Fair Value
Derivative Liability, Fair Value, Gross Liability		6
Interest rate derivatives | Designated as Hedging Instrument | Other Assets
Derivatives, Fair Value
Derivative Asset, Fair Value, Gross Asset	[1]	0	2
Derivative Asset, Fair Value, Gross Liability	[1]	0	0
Interest rate derivatives | Designated as Hedging Instrument | Accrued Liabilities
Derivatives, Fair Value
Derivative Liability, Fair Value, Gross Liability	[1]	0	5
Derivative Liability, Fair Value, Gross Asset	[1]	0	0
Interest rate derivatives | Designated as Hedging Instrument | Other Noncurrent Liabilities
Derivatives, Fair Value
Derivative Liability, Fair Value, Gross Liability	[1]	6	1
Derivative Liability, Fair Value, Gross Asset	[1]	$ 0	$ 0
[1]	Represents the position of each trade before consideration of offsetting positions with each counterparty and does not include the impact of cash collateral deposits provided to or received from counterparties. See discussion of credit risk and collateral following in this Note.

Financial Derivative Instrume_6

Financial Derivative Instruments - Collateral by Balance Sheet Location (Details) - Fuel derivatives - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Collateral Already Posted, Aggregate Fair Value	$ 34
Prepaid expenses and other current assets
Derivative [Line Items]
Total Collateral Already Received Aggregate Fair Value	3	$ 10
Other Assets
Derivative [Line Items]
Total Collateral Already Received Aggregate Fair Value	$ 31	$ 15

Financial Derivative Instrume_7

Financial Derivative Instruments - Offsetting of Derivative Assets (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Offsetting Assets
Asset derivative contracts, net		$ 90	$ 49
Fuel derivatives | Prepaid expenses and other current assets
Offsetting Assets
Gross amounts of recognized assets		13	48
Gross amounts offset in the Balance Sheet		(3)	(10)
Asset derivative contracts, net		10	38
Fuel derivatives | Other Assets
Offsetting Assets
Gross amounts of recognized assets		121	62
Gross amounts offset in the Balance Sheet		(31)	(15)
Asset derivative contracts, net	[1]	90	47
Interest rate derivatives | Other Assets
Offsetting Assets
Gross amounts of recognized assets		0	2
Gross amounts offset in the Balance Sheet		0	0
Asset derivative contracts, net	[1]	$ 0	$ 2
[1]	The net amounts of derivative assets and liabilities are reconciled to the individual line item amounts presented in the Consolidated Balance Sheet in Note 16.

Financial Derivative Instrume_8

Financial Derivative Instruments - Offsetting of Derivative Liabilities (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Fuel derivatives | Prepaid expenses and other current assets
Offsetting Liabilities
Gross amounts of recognized liabilities		$ 3	$ 10
Gross amounts offset in the Balance Sheet		(3)	(10)
Liabilities derivative contracts, net		0	0
Fuel derivatives | Other Assets
Offsetting Liabilities
Gross amounts of recognized liabilities		31	15
Gross amounts offset in the Balance Sheet		(31)	(15)
Liabilities derivative contracts, net	[1]	0	0
Interest rate derivatives | Accrued Liabilities
Offsetting Liabilities
Gross amounts of recognized liabilities		0	5
Gross amounts offset in the Balance Sheet		0	0
Liabilities derivative contracts, net		0	5
Interest rate derivatives | Other Noncurrent Liabilities
Offsetting Liabilities
Gross amounts of recognized liabilities		6	1
Gross amounts offset in the Balance Sheet		0	0
Liabilities derivative contracts, net		$ 6	$ 1
[1]	The net amounts of derivative assets and liabilities are reconciled to the individual line item amounts presented in the Consolidated Balance Sheet in Note 16.

Financial Derivative Instrume_9

Financial Derivative Instruments - (Gain) Loss in Income by Hedging Relationship (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Interest Expense
Derivative [Line Items]
(Gain) Loss on Derivative Instruments, Net, Pretax	$ 6	$ 29
Fuel
Derivative [Line Items]
(Gain) Loss on Derivative Instruments, Net, Pretax	70	48
Other (gains) losses, net
Derivative [Line Items]
(Gain) Loss on Derivative Instruments, Net, Pretax	39
Cash Flow Hedging | Interest Expense | Fuel derivatives
Derivative [Line Items]
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0
Cash Flow Hedging | Interest Expense | Interest rate derivatives
Derivative [Line Items]
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into Income, Effective Portion, Net	1	5
Cash Flow Hedging | Fuel | Fuel derivatives
Derivative [Line Items]
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into Income, Effective Portion, Net	70	48
Cash Flow Hedging | Fuel | Interest rate derivatives
Derivative [Line Items]
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0
Cash Flow Hedging | Other (gains) losses, net | Fuel derivatives
Derivative [Line Items]
Loss on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring	39
Cash Flow Hedging | Other (gains) losses, net | Interest rate derivatives
Derivative [Line Items]
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into Income, Effective Portion, Net	0
Not Designated as Hedging Instrument | Fuel derivatives
Derivative [Line Items]
Loss on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring	39
Not Designated as Hedging Instrument | Fair Value Hedging | Interest Expense | Interest rate derivatives
Derivative [Line Items]
Interest Expense, Debt	11	22
Not Designated as Hedging Instrument | Fair Value Hedging | Fuel | Interest rate derivatives
Derivative [Line Items]
Interest Expense, Debt	0	0
Not Designated as Hedging Instrument | Fair Value Hedging | Other (gains) losses, net | Interest rate derivatives
Derivative [Line Items]
Interest Expense, Debt	0
Designated as Hedging Instrument | Fair Value Hedging | Interest Expense | Interest rate derivatives
Derivative [Line Items]
(Gain) Loss on Derivative Instruments, Net, Pretax	(6)	2
Designated as Hedging Instrument | Fair Value Hedging | Fuel | Interest rate derivatives
Derivative [Line Items]
(Gain) Loss on Derivative Instruments, Net, Pretax	0	$ 0
Designated as Hedging Instrument | Fair Value Hedging | Other (gains) losses, net | Interest rate derivatives
Derivative [Line Items]
(Gain) Loss on Derivative Instruments, Net, Pretax	$ 0

Financial Derivative Instrum_10

Financial Derivative Instruments - (Gain) Loss by Hedging Relationship (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash Flow Hedging
Derivative Instruments, (Gain) Loss
(Gain) loss recognized in AOCI on derivatives (effective portion)	$ 106	$ 119
Not Designated as Hedging Instrument | Other Nonoperating Income (Expense)
Derivative Instruments, (Gain) Loss
(Gain) loss recognized in income on derivatives	29	0
Fuel derivatives | Cash Flow Hedging
Derivative Instruments, (Gain) Loss
(Gain) loss recognized in AOCI on derivatives (effective portion)	80	90
Fuel derivatives | Not Designated as Hedging Instrument | Other Nonoperating Income (Expense)
Derivative Instruments, (Gain) Loss
(Gain) loss recognized in income on derivatives	1	0
Interest rate derivatives | Cash Flow Hedging
Derivative Instruments, (Gain) Loss
(Gain) loss recognized in AOCI on derivatives (effective portion)	26	29
Interest rate derivatives | Not Designated as Hedging Instrument | Other Nonoperating Income (Expense)
Derivative Instruments, (Gain) Loss
(Gain) loss recognized in income on derivatives	$ 28	$ 0

Financial Derivative Instrum_11

Financial Derivative Instruments - Premiums for Fuel Derivative Contracts (Details) - Fuel derivatives - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Designated as Hedging Instrument | Operating Expense
Derivative [Line Items]
Premiums paid for fuel derivative contracts	$ 64	$ 95	$ 135
Not Designated as Hedging Instrument, Economic Hedge | Other (gains) losses, net
Derivative [Line Items]
Premiums paid for fuel derivative contracts	$ 34	$ 0	$ 0

Financial Derivative Instrum_12

Financial Derivative Instruments - Fair Values of Fuel Derivatives Amounts Posted as Collateral (Details) $ in Millions	Dec. 31, 2020USD ($)
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Maximum Sum Of Derivatives Of Counterparty To Be Included In Other	$ 10
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Cash Collateral Percent Of Fair Value Fuel Derivatives Contracts	100.00%
Letter of Credit Percent of Collateral	100.00%
Fuel derivatives
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Fair value of fuel derivatives - asset	$ 134
Collateral Already Posted, Aggregate Fair Value	34
Letters of credit (LC)	0
Counterparty A | Fuel derivatives
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Fair value of fuel derivatives - asset	33
Collateral Already Posted, Aggregate Fair Value	34
Letters of credit (LC)	0
Counterparty A | Minimum | Fuel derivatives
If credit rating is investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(100)
Fair value of fuel derivative level at which cash is received from CP	0	[1]
Fair value of fuel derivative levels at which cash is pledged to CP	(200)	[2]
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	0
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2	(600)
Fair value of fuel derivative level at which cash is received from CP		[3]
Fair value of fuel derivative level at which cash is pledged to CP	(200)
Counterparty A | Maximum | Fuel derivatives
If credit rating is investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is pledged to CP	(600)	[2]
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(200)
Fair value of fuel derivative level at which cash is pledged to CP	(600)
Counterparty B | Fuel derivatives
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Fair value of fuel derivatives - asset	15
Collateral Already Posted, Aggregate Fair Value	0
Letters of credit (LC)	0
Counterparty B | Minimum | Fuel derivatives
If credit rating is investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(50)
Fair value of fuel derivative level at which cash is received from CP	150	[1]
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1		[3]
Fair value of fuel derivative level at which cash is received from CP		[3]
Counterparty C | Fuel derivatives
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Fair value of fuel derivatives - asset	33
Collateral Already Posted, Aggregate Fair Value	0
Letters of credit (LC)	0
Counterparty C | Minimum | Fuel derivatives
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Option to substitute LC for cash Threshold 1	(75)	[4]
Option to substitute LC for cash Threshold 2	(550)	[4]
If credit rating is investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(75)	[1]
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2	(550)	[1]
Fair value of fuel derivative level at which cash is received from CP	250	[1]
Fair value of fuel derivative levels at which cash is pledged to CP	(150)	[4]
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	0
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2	(550)
Fair value of fuel derivative level at which cash is received from CP		[3]
Fair value of fuel derivative level at which cash is pledged to CP	(150)
Counterparty C | Maximum | Fuel derivatives
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Option to substitute LC for cash Threshold 1	(150)	[4]
If credit rating is investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(150)	[1]
Fair value of fuel derivative levels at which cash is pledged to CP	(550)	[4]
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(150)
Fair value of fuel derivative level at which cash is pledged to CP	(550)
Counterparty D | Fuel derivatives
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Fair value of fuel derivatives - asset	14
Collateral Already Posted, Aggregate Fair Value	0
Letters of credit (LC)	0
Counterparty D | Minimum | Fuel derivatives
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Option to substitute LC for cash Threshold 1	(125)	[5]
Option to substitute LC for cash Threshold 2	(550)	[5]
If credit rating is investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(125)	[1]
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2	(550)	[1]
Fair value of fuel derivative level at which cash is received from CP	(125)	[1]
Fair value of fuel derivative levels at which cash is pledged to CP	(150)	[4]
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	0
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2	(550)
Fair value of fuel derivative level at which cash is received from CP		[3]
Fair value of fuel derivative level at which cash is pledged to CP	(150)
Counterparty D | Maximum | Fuel derivatives
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Option to substitute LC for cash Threshold 1	(150)	[5]
If credit rating is investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(150)	[1]
Fair value of fuel derivative levels at which cash is pledged to CP	(550)	[4]
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(150)
Fair value of fuel derivative level at which cash is pledged to CP	(550)
Counterparty E | Fuel derivatives
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Fair value of fuel derivatives - asset	17
Collateral Already Posted, Aggregate Fair Value	0
Letters of credit (LC)	0
Counterparty E | Minimum | Fuel derivatives
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Option to substitute LC for cash Threshold 1		[5]
If credit rating is investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(40)
Fair value of fuel derivative level at which cash is received from CP	100	[1]
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1		[3]
Fair value of fuel derivative level at which cash is received from CP		[3]
Counterparty F | Fuel derivatives
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Fair value of fuel derivatives - asset	11
Collateral Already Posted, Aggregate Fair Value	0
Letters of credit (LC)	0
Counterparty F | Minimum | Fuel derivatives
If credit rating is investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(65)	[1]
Fair value of fuel derivative level at which cash is received from CP	70	[1]
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1		[3]
Fair value of fuel derivative level at which cash is received from CP		[3]
Counterparty Other | Fuel derivatives
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Fair value of fuel derivatives - asset	11	[6]
Collateral Already Posted, Aggregate Fair Value	0	[6]
Letters of credit (LC)	$ 0	[6]
[1]	Thresholds may vary based on changes in credit ratings within investment grade.
[2]	The Company has the option of providing cash as collateral.
[3]	Cash collateral is provided at 100 percent of fair value of fuel derivative contracts.
[4]	The Company has the option of providing cash or letters of credit as collateral.
[5]	The Company has the option to substitute letters of credit for 100 percent of cash collateral requirement.
[6]	Individual counterparties with fair value of fuel derivatives <$10 million.

Fair Value Measurements Narrati

Fair Value Measurements Narrative (Details)	12 Months Ended
	Dec. 31, 2020Agreements
Fair Value Disclosures [Abstract]
Debt agreements not publicly held	4

Fair Value Measurements - Measu

Fair Value Measurements - Measured on Recurring Basis (Details) - USD ($)		Dec. 31, 2020		Dec. 31, 2019
Assets
Time Deposits		$ 425,000,000
Fuel derivatives:
Derivative Asset, Fair Value, Gross Asset		134,000,000		$ 112,000,000
Fuel derivatives:
Derivative Liability, Fair Value, Gross Liability		(6,000,000)		(6,000,000)
Quoted prices in active markets for identical assets (Level 1)
Assets
Time Deposits		0
Significant other observable inputs (Level 2)
Assets
Time Deposits		425,000,000
Significant unobservable inputs (Level 3)
Assets
Time Deposits		0
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1)
Assets
Treasury bills		1,800,000,000		1,196,000,000
Interest rate derivatives (see Note 10)				0
Fuel derivatives:
Other available for sale securities		259,000,000	[1]	197,000,000
Assets, Fair Value Disclosure		12,722,000,000		3,392,000,000
Fuel derivatives:
Interest rate derivatives (see Note 11)		0		0
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2)
Assets
Treasury bills		0		0
Interest rate derivatives (see Note 10)				2,000,000
Fuel derivatives:
Other available for sale securities		0	[1]	0
Assets, Fair Value Disclosure		871,000,000		879,000,000
Fuel derivatives:
Interest rate derivatives (see Note 11)		(6,000,000)		(6,000,000)
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3)
Assets
Treasury bills		0		0
Interest rate derivatives (see Note 10)				0
Fuel derivatives:
Other available for sale securities		0	[1]	0
Assets, Fair Value Disclosure		134,000,000		110,000,000
Fuel derivatives:
Interest rate derivatives (see Note 11)		0		0
Cash Equivalents | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1)
Assets
Cash equivalents	[2]	10,663,000,000		1,999,000,000
Cash Equivalents | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2)
Assets
Cash equivalents	[2]	0		0
Cash Equivalents | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3)
Assets
Cash equivalents	[2]	0		0
Commercial paper | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1)
Assets
Cash equivalents		0		0
Commercial paper | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2)
Assets
Cash equivalents		90,000,000		535,000,000
Commercial paper | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3)
Assets
Cash equivalents		0		0
Certificates of deposit | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1)
Assets
Cash equivalents		0		0
Investments				0
Certificates of deposit | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2)
Assets
Cash equivalents		10,000,000		14,000,000
Investments				268,000,000
Certificates of deposit | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3)
Assets
Cash equivalents		0		0
Investments				0
Time deposits | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1)
Assets
Cash equivalents		0
Investments				0
Time deposits | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2)
Assets
Cash equivalents		300,000,000
Investments				60,000,000
Time deposits | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3)
Assets
Cash equivalents		0
Investments				0
Certificates of deposit | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1)
Assets
Investments		0
Certificates of deposit | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2)
Assets
Investments		46,000,000
Certificates of deposit | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3)
Assets
Investments		0
Options Held | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1)
Fuel derivatives:
Derivative Asset, Fair Value, Gross Asset	[3]	0		0
Options Held | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2)
Fuel derivatives:
Derivative Asset, Fair Value, Gross Asset	[3]	0		0
Options Held | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3)
Fuel derivatives:
Derivative Asset, Fair Value, Gross Asset	[3]	134,000,000		110,000,000
Period end date | Fair Value, Measurements, Recurring
Assets
Treasury bills		1,800,000,000		1,196,000,000
Interest rate derivatives (see Note 10)				2,000,000
Fuel derivatives:
Other available for sale securities		259,000,000	[1]	197,000,000
Assets, Fair Value Disclosure		13,727,000,000		4,381,000,000
Fuel derivatives:
Interest rate derivatives (see Note 11)		(6,000,000)		(6,000,000)
Period end date | Cash Equivalents | Fair Value, Measurements, Recurring
Assets
Cash equivalents	[2]	10,663,000,000		1,999,000,000
Period end date | Commercial paper | Fair Value, Measurements, Recurring
Assets
Cash equivalents		90,000,000		535,000,000
Period end date | Certificates of deposit | Fair Value, Measurements, Recurring
Assets
Cash equivalents		10,000,000		14,000,000
Investments				268,000,000
Period end date | Time deposits | Fair Value, Measurements, Recurring
Assets
Cash equivalents		300,000,000
Investments				60,000,000
Period end date | Certificates of deposit | Fair Value, Measurements, Recurring
Assets
Investments		46,000,000
Period end date | Options Held | Fair Value, Measurements, Recurring
Fuel derivatives:
Derivative Asset, Fair Value, Gross Asset	[3]	$ 134,000,000		$ 110,000,000
[1]	In the Consolidated Balance Sheet amounts are presented as an asset. See Note 11.
[2]	Cash equivalents are primarily composed of money market investments.
[3]	In the Consolidated Balance Sheet amounts are presented as an asset. See Note 11.

Fair Value Measurement - Fair V

Fair Value Measurement - Fair Value Assets and Liabilities Measured on Recurring Basis with Unobservable Inputs (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total losses (realized or unrealized) included in other comprehensive income (loss)				$ (112)
Fuel derivatives
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance				138
Losses for the period included in earnings	[1]	$ (40)
Fair Value, Recurring Basis, Unobservable Input Reconciliation, Asset (Liability), Gain (Loss), OCI		(65)
Purchases		129	[2]	133	[3]
Sales	[3]			(2)
Settlements				(47)
Ending Balance		134		$ 110
Fuel derivatives | Commodity Option [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
The amount of total losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held at December 31, 2020	[1]	(15)
The amount of total losses for the period included in other comprehensive loss attributable to the change in unrealized gains or losses relating to assets still held at December 31, 2020		$ (41)
[1]	Included in Other (gains) losses, net, within the Consolidated Statement of Comprehensive Income (Loss).
[2]	The purchase of fuel derivatives is recorded gross based on the structure of the derivative instrument and whether a contract with multiple derivatives was purchased as a single instrument or separate instruments.
[3]	The purchase and sale of fuel derivatives are recorded gross based on the structure of the derivative instrument and whether a contract with multiple derivatives was purchased as a single instrument or separate instruments.

Fair Value Measurements - Quant

Fair Value Measurements - Quantitative Information about Level 3 Fair Value (Details) - Fuel derivatives - Significant unobservable inputs (Level 3) - Measurement Input, Option Volatility [Member]	Dec. 31, 2020
2021 | Maximum
Quantitative Information About Level 3 [Line Items]
Derivative Asset, Measurement Input	0.43
2021 | Weighted Average [Member]
Quantitative Information About Level 3 [Line Items]
Derivative Asset, Measurement Input	0.33
2021 | Minimum
Quantitative Information About Level 3 [Line Items]
Derivative Asset, Measurement Input	0.29
2022 | Maximum
Quantitative Information About Level 3 [Line Items]
Derivative Asset, Measurement Input	0.32
2022 | Weighted Average [Member]
Quantitative Information About Level 3 [Line Items]
Derivative Asset, Measurement Input	0.28
2022 | Minimum
Quantitative Information About Level 3 [Line Items]
Derivative Asset, Measurement Input	0.25
2023 | Maximum
Quantitative Information About Level 3 [Line Items]
Derivative Asset, Measurement Input	0.26
2023 | Weighted Average [Member]
Quantitative Information About Level 3 [Line Items]
Derivative Asset, Measurement Input	0.25
2023 | Minimum
Quantitative Information About Level 3 [Line Items]
Derivative Asset, Measurement Input	0.23
Beyond 2023 | Maximum
Quantitative Information About Level 3 [Line Items]
Derivative Asset, Measurement Input	0.26
Beyond 2023 | Weighted Average [Member]
Quantitative Information About Level 3 [Line Items]
Derivative Asset, Measurement Input	0.25
Beyond 2023 | Minimum
Quantitative Information About Level 3 [Line Items]
Derivative Asset, Measurement Input	0.25

Fair Value Instruments - Carryi

Fair Value Instruments - Carrying and Estimated Fair Value of Debt (Details) - USD ($) $ in Millions	Dec. 31, 2020	Jul. 31, 2020	May 04, 2020	May 01, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Debt and Lease Obligation	$ 10,381				$ 2,678
2.65% Notes due 2020
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)	2.65%
2.65% Notes due 2020 | Unsecured Debt
Debt Instrument [Line Items]
Carrying amount of debt	$ 0				500
Interest rate stated in the debt agreement (in hundredths)	2.65%
Term Loan Agreement Due 2020 [Member]
Debt Instrument [Line Items]
Secured Debt - Carrying Value	$ 0				$ 134
Interest rate stated in the debt agreement (in hundredths)	5.223%				5.223%
Unsecured Senior Notes Due 2022 - 2.75%
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)	2.75%
Unsecured Senior Notes Due 2022 - 2.75% | Unsecured Debt
Debt Instrument [Line Items]
Carrying amount of debt	$ 300				$ 300
Interest rate stated in the debt agreement (in hundredths)	2.75%
Total Pass Through Certificates [Member] | Enhanced Equipment Trust Certificate
Debt Instrument [Line Items]
Carrying amount of debt	$ 137				197
Interest rate stated in the debt agreement (in hundredths)	6.24%
Term Loan Agreement Due 2026 - 3.03%
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)	1.34%
Term Loan Agreement Due 2026 - 3.03% | Notes Payable to Banks
Debt Instrument [Line Items]
Carrying amount of debt	$ 159				178
Interest rate stated in the debt agreement (in hundredths)	1.34%
Unsecured Senior Notes Due 2026 - 3.00%
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)	3.00%
Unsecured Senior Notes Due 2026 - 3.00% | Unsecured Debt
Debt Instrument [Line Items]
Carrying amount of debt	$ 300				300
Interest rate stated in the debt agreement (in hundredths)	3.00%
Unsecured Senior Notes Due 2027 - 3.45%
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)	3.45%
Unsecured Senior Notes Due 2027 - 3.45% | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)	3.45%
7.375% Debentures due 2027
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)	7.375%
7.375% Debentures due 2027 | Unsecured Debt
Debt Instrument [Line Items]
Carrying amount of debt	$ 119				122
Interest rate stated in the debt agreement (in hundredths)	7.375%
4.750 Unsecured Notes due 2023
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)			4.75%
4.750 Unsecured Notes due 2023 | Unsecured Debt
Debt Instrument [Line Items]
Carrying amount of debt	$ 1,250				0
Interest rate stated in the debt agreement (in hundredths)	4.75%
1.250 Convertible Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)				1.25%
1.250 Convertible Senior Notes due 2025 [Member] | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)	1.25%
1.250 Convertible Senior Notes due 2025 [Member] | 1.25% convertible notes (a)
Debt Instrument [Line Items]
Carrying amount of debt	$ 1,945				0
Interest rate stated in the debt agreement (in hundredths)				1.25%
5.250 Unsecured Notes due 2025 | Unsecured Debt
Debt Instrument [Line Items]
Carrying amount of debt	$ 1,550	$ 300			0
Interest rate stated in the debt agreement (in hundredths)	5.25%
Term Loan Agreement Due 2025 [Member] | Notes Payable to Banks
Debt Instrument [Line Items]
Carrying amount of debt	$ 119				0
Interest rate stated in the debt agreement (in hundredths)	1.65%
3.45 Unsecured Senior Notes due 2027 [Member] | Unsecured Debt
Debt Instrument [Line Items]
Carrying amount of debt	$ 300				300
5.125 Notes due 2027 | Unsecured Debt
Debt Instrument [Line Items]
Carrying amount of debt	$ 2,000	$ 700			0
Interest rate stated in the debt agreement (in hundredths)	5.125%
1.65 Term Loan Agreement Payable through 2028 [Member] | Notes Payable to Banks
Debt Instrument [Line Items]
Carrying amount of debt	$ 184				0
2.625% Notes due 2030 | Unsecured Debt
Debt Instrument [Line Items]
Carrying amount of debt	$ 500				0
Interest rate stated in the debt agreement (in hundredths)	2.625%
1.0 Payroll Support Program Loan due 2030 | Unsecured Debt
Debt Instrument [Line Items]
Carrying amount of debt	$ 976				0
Interest rate stated in the debt agreement (in hundredths)	1.00%
Term Loan Agreement Due 2028 [Member] | Notes Payable to Banks
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)	1.65%
Level 2 | Unsecured Senior Notes Due 2022 - 2.75% | Unsecured Debt
Debt Instrument [Line Items]
Notes Payable, Fair Value	$ 311
Level 2 | Total Pass Through Certificates [Member] | Enhanced Equipment Trust Certificate
Debt Instrument [Line Items]
Notes Payable, Fair Value	140
Level 2 | Unsecured Senior Notes Due 2026 - 3.00% | Unsecured Debt
Debt Instrument [Line Items]
Notes Payable, Fair Value	324
Level 2 | 7.375% Debentures due 2027 | Unsecured Debt
Debt Instrument [Line Items]
Loans Payable, Fair Value	145
Level 2 | 4.750 Unsecured Notes due 2023
Debt Instrument [Line Items]
Notes Payable, Fair Value	1,362
Level 2 | 1.250 Convertible Senior Notes due 2025 [Member] | 1.25% convertible notes (a)
Debt Instrument [Line Items]
Notes Payable, Fair Value	3,359
Level 2 | 5.250 Unsecured Notes due 2025
Debt Instrument [Line Items]
Notes Payable, Fair Value	1,799
Level 2 | 3.45 Unsecured Senior Notes due 2027 [Member] | Unsecured Debt
Debt Instrument [Line Items]
Notes Payable, Fair Value	329
Level 2 | 5.125 Notes due 2027 | Unsecured Debt
Debt Instrument [Line Items]
Notes Payable, Fair Value	2,383
Level 2 | 2.625% Notes due 2030 | Unsecured Debt
Debt Instrument [Line Items]
Notes Payable, Fair Value	515
Level 3 | Term Loan Agreement Due 2026 - 3.03% | Notes Payable to Banks
Debt Instrument [Line Items]
Loans Payable, Fair Value	155
Level 3 | Term Loan Agreement Due 2025 [Member] | Notes Payable to Banks
Debt Instrument [Line Items]
Loans Payable, Fair Value	119
Level 3 | 1.65 Term Loan Agreement Payable through 2028 [Member] | Notes Payable to Banks
Debt Instrument [Line Items]
Loans Payable, Fair Value	183
Level 3 | 1.0 Payroll Support Program Loan due 2030 | Unsecured Debt
Debt Instrument [Line Items]
Loans Payable, Fair Value	953
AirTran Airways | 737 Aircraft Notes payable through 2020
Debt Instrument [Line Items]
Secured Debt - Carrying Value	$ 0				$ 20

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fuel derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (125)	$ (56)
Changes in fair value	(103)	(117)
Ending balance	(119)	(125)
Interest rate derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(33)	0
Changes in fair value	(34)	(38)
Reclassification to earnings	1	5
Ending balance	(66)	(33)
Defined benefit plan items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	20	58
Changes in fair value	(63)	(38)
Reclassification to earnings	0	0
Ending balance	(43)	20
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	59	25
Changes in fair value	32	34
Reclassification to earnings	0	0
Ending balance	91	59
Deferred tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	18	(7)
Changes in fair value	39	37
Reclassification to earnings	(25)	(12)
Ending balance	32	18
Accumulated other comprehensive income (loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(61)	20
Changes in fair value	(129)	(122)
Reclassification to earnings	85	41
Ending balance	(105)	(61)
Reclassification out of Accumulated Other Comprehensive Income | Fuel derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification to earnings	$ 109	$ 48

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Income (Loss) - Reclassification out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Fuel and oil	$ 1,849	$ 4,347	$ 4,616
Other (gains) losses, net	158	8	18
Less: Tax Expense	(1,182)	657	$ 699
Interest rate derivatives
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	1	5
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax	85
Reclassification out of Accumulated Other Comprehensive Income | Fuel derivatives
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	109	$ 48
Less: Tax Expense	25
Net of tax	84
Fuel derivatives | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Fuel and oil	70
Other (gains) losses, net	39
Interest rate derivatives | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Less: Tax Expense	0
Net of tax	$ 1

Employee Retirement Plans (Deta

Employee Retirement Plans (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined contribution plans [Abstract]
Company contributions to all defined contribution plans expensed		$ 561	$ 1,200	$ 1,000
Maximum age after retirement that employees may use accrued unused sick time to pay for medical and dental premiums		65 years
Change in benefit obligation [Roll Forward]
APBO at beginning of period		$ 288	232
Service cost		22	17	18
Interest cost		10	10	9
Benefits paid		(10)	(9)
Actuarial loss		63	(38)
Plan amendments		53	0
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits		2	0
APBO at end of period		428	288	232
Estimated future benefit payments time period [Abstract]
2021		24
2022		25
2023		24
2024		24
2025		26
Next five years thereafter		146
Reconciliation of funded status to accrued postretirement benefit cost recognized on the balance sheet [Abstract]
Funded status		(428)	(288)
Unrecognized net actuarial (gain) loss		40	(24)
Unrecognized prior service cost		3	4
Accumulated other comprehensive income (loss)		(43)	20
Consolidated Balance Sheet liability		(428)	(288)
Components of periodic postretirement benefit cost [Abstract]
Service cost		22	17	18
Interest cost		10	10	9
Amortization of prior service cost		1	1	3
Amortization of net gain		0	(2)	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment		53	0	0
Defined Benefit Plan, Other Cost (Credit)		2	0	0
Net periodic postretirement benefit cost		$ 88	$ 26	$ 30
Actuarial assumptions used to account for postretirement benefit plans [Abstract]
Weighted-average discount rate (in hundredths)		2.45%	3.30%	4.35%
Assumed healthcare cost trend rates [Abstract]
Assumed healthcare cost trend rate decline (in hundredths)	[1]	6.75%	7.13%	7.13%
Assumed healthcare cost trend rate	[1]	6.50%
Defined Benefit Plan, Health Care Cost Trend Rate Reached in 2028		4.75%
[1]	The assumed healthcare cost trend rate is expected to be 6.50% for 2021, then decline gradually to 4.75% by 2028 and remain level thereafter.

Income Taxes (Detail)

Income Taxes (Detail) $ in Millions		12 Months Ended
		Dec. 31, 2020USD ($)aircraft		Dec. 31, 2019USD ($)		Dec. 31, 2018USD ($)	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		27.80%		22.20%			35.00%
Deferred Tax Assets, State Taxes		$ 852
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Percent						0.21
CARES Act Loss Carryback Period		5 years
Operating Loss Carryforward Expiration Year 2025 | aircraft		2,025
Operating Loss Carryforward Expiration Year 2040 | aircraft		2,040
DEFERRED TAX LIABILITIES:
Accelerated depreciation		$ 2,939		$ 3,096
Prepaid insurance		190		12
Operating lease right-of-use assets		423		293
Other		67		81
Total deferred tax liabilities		3,619		3,482
DEFERRED TAX ASSETS:
Accrued employee benefits		491		346
Rapid rewards loyalty liability		632		305
Operating lease liabilities		443		308
Residual travel funds		117		0
Construction obligation		72		38
Net operating losses and tax credits		60	[1]	8
Other		170		113
Total deferred tax assets		1,985		1,118
Net deferred tax liability		1,634		2,364
CURRENT:
Federal	[2]	(273)		610		$ 338
State		(5)		102		60
Change in federal statutory rate	[3]	(188)		0		0
Total current		(466)		712		398
DEFERRED:
Federal	[2]	(589)		(18)		299
State		(76)		(6)		2
State net operating losses		(51)		0		0
Change in federal statutory tax rate	[4]	0		(31)		0
Total deferred		(716)		(55)		301
Total		(1,182)		657		699
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Tax at statutory U.S. tax rates		(894)		621		664
State income taxes, net of federal benefit		(115)		76		49
Change in federal statutory rate		(188)	[3]	(31)	[4]	0
Other, net		15		(9)		(14)
PROVISION (BENEFIT) FOR INCOME TAXES		$ (1,182)		$ 657		$ 699
[1]	At December 31, 2020, the Company had approximately $852 million of state net operating loss carryforwards to reduce future state taxable income. These state net operating loss carryforwards will expire in years 2025 - 2040 if unused.
[2]	The CARES Act allows entities to carry back 2020 losses to prior periods of up to five years, and claim refunds of federal taxes paid, and the Company expects to receive a significant cash tax refund once it completes all the necessary requirements to make the appropriate filings with the IRS.
[3]	The benefit is representative of the excess refund generated as the result of carrying the 2020 losses back to a period when the federal statutory tax rate was 35 percent as opposed to the current tax rate of 21 percent.
[4]	The Tax Cuts and Jobs Act was enacted in December 2017, which reduced the U.S. federal corporate tax rate from the previous rate of 35 percent to 21 percent

Supplemental Financial Inform_3

Supplemental Financial Information - Accounts and Other Receivables (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020		Dec. 31, 2019
Accounts and Other Receivables [Abstract]
Trade receivables	$ 46		$ 53
Credit card receivables	35		112
Business partners and other suppliers	274		779
Taxes receivable	740	[1]	87
Other	35		55
Accounts and other receivables	1,130		$ 1,086
Cash Tax Refund Expected From CARES Act Loss Carry Back Provision	$ 470
CARES Act Loss Carryback Period	5 years
[1]	This amount includes approximately $470 million associated with a significant cash tax refund expected as a result of the CARES Act allowing entities to carry back 2020 losses to prior periods of up to five years, and claim refunds of federal taxes paid. This amount also includes excise taxes remitted to taxing authorities for which the subsequent flights were canceled by Customers, resulting in amounts due back to the Company. See Note 15 for further information.

Supplemental Financial Inform_4

Supplemental Financial Information - Other Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Other Assets [Abstract]
Derivative contracts	$ 90	$ 49
Intangible assets, net	295	296
Other	337	232
Other assets	$ 722	$ 577

Supplemental Financial Inform_5

Supplemental Financial Information - Accounts Payable (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Accounts Payable [Abstract]
Accounts payable trade	$ 111	$ 304
Salaries payable	201	231
Taxes payable excluding income taxes	49	227
Aircraft maintenance payable	95	162
Fuel payable	66	129
Dividends payable	0	93
Other payable	409	428
Accounts payable	$ 931	$ 1,574

Supplemental Financial Inform_6

Supplemental Financial Information - Accrued Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020		Dec. 31, 2019
Supplemental Financial Data [Line Items]
Extended Emergency Time Off	$ 393		$ 0
Voluntary Separation Program 2020	143		0
Profitsharing and savings plans	25		695
Vendor Prepayment	600	[1]	0
Vacation pay	436		434
Health	111		120
Workers compensation	161		166
Property and income taxes	84		79
Interest	49		16
Other	257		239
Accrued liabilities	$ 2,259		$ 1,749
[1]	In fourth quarter 2020, the Company received a $600 million prepayment from Chase for Rapid Rewards points expected to be purchased during 2021, based on cardholder activity on its Visa card associated with its loyalty program. The Company currently expects the majority of this amount to be reclassified to deferred revenue in Air Traffic liability--loyalty during the first half of 2021.

Supplemental Financial Inform_7

Supplemental Financial Information - Other Non-Current Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Other Liabilities, Noncurrent [Abstract]
Extended Emergency Time Off	$ 57	$ 0
Voluntary Separation Program 2020	321	0
Postretirement obligation	428	288
Other deferred compensation	353	313
Other	88	105
Other non-current liabilities	$ 1,247	$ 706

Boeing 737 MAX Aircraft Groun_2

Boeing 737 MAX Aircraft Grounding (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)aircraft	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Number of Aircraft Grounded Under Emergency Order on March 13, 2019	34
After-Tax Potential Concessions and Other Considerations Announced July 2019 | $	$ 4,900
Pre-Tax Potential Concessions and Other Considerations Announced January 2020 | $	$ 2,600
Number of Aircraft Not Delivered Due to Grounding Under Emergency Order	41
Supplier Proceeds | $	$ 428	$ 400	$ 0
Contract to Own Aircraft
Number of Aircraft Not Delivered Due to Grounding Under Emergency Order	28
Contract to Lease Aircraft
Number of Aircraft Not Delivered Due to Grounding Under Emergency Order	13
737 MAX 8
Property, Plant and Equipment, Number of Aircraft Leased	7

Quarterly Financial Data (Detai

Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019		Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Data [Abstract]
Operating revenues	$ 2,013	$ 1,793	$ 1,008	$ 4,234	$ 5,729		$ 5,639	$ 5,909	$ 5,149
Operating income (loss)	(1,169)	(1,411)	(1,127)	(110)	665		819	968	505	$ (3,816)	$ 2,957	$ 3,206
INCOME (LOSS) BEFORE INCOME TAXES	(1,331)	(1,542)	(1,239)	(144)	666		819	968	504	(4,256)	2,957	3,164
Net income (loss)	$ (908)	$ (1,157)	$ (915)	$ (94)	$ 514	[1]	$ 659	$ 741	$ 387	$ (3,074)	$ 2,300	$ 2,465
NET INCOME (LOSS) PER SHARE, BASIC	$ (1.54)	$ (1.96)	$ (1.63)	$ (0.18)	$ 0.98	[1]	$ 1.24	$ 1.37	$ 0.70	$ (5.44)	$ 4.28	$ 4.30
NET INCOME (LOSS) PER SHARE, DILUTED	$ (1.54)	$ (1.96)	$ (1.63)	$ (0.18)	$ 0.98	[1]	$ 1.23	$ 1.37	$ 0.70	$ (5.44)	$ 4.27	$ 4.29
Discretionary Profitsharing Related to Impact of Aircraft Grounded Under Emergency Order					$ 124
Net Income Impact of 2019 Discretionary Profitsharing					$ 97
Net Income per Share Impact of 2019 Discretionary Profitsharing					$ 0.18
[1]	In addition to the ongoing impact of the Boeing 737 MAX aircraft ("MAX") grounding that impacted all four quarters of 2019, fourth quarter 2019 also included the impact of the pre-tax $124 million discretionary, special profitsharing award accrual authorized by the Company's Board of Directors during fourth quarter 2019 for compensation received from Boeing related to the Company's estimated 2019 financial damages related to the grounding of the Boeing 737 MAX. See Note 17 to the Consolidated Financial Statements for further information on the MAX groundings. The impact of this accrual resulted in a decrease to Net income of approximately $97 million and reduced Basic and Diluted net income per share by approximately $.18 for the fourth quarter 2019.