United Airlines 10-K 22 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 14, 2018	Jun. 30, 2017
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	UAL
Entity Registrant Name	United Continental Holdings, Inc.
Entity Central Index Key	100,517
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		284,700,547
Entity Public Float			$ 21,673,390,018
United Airlines, Inc.
Document Information [Line Items]
Entity Registrant Name	United Airlines, Inc.
Entity Central Index Key	319,687
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		1,000

Statements of Consolidated Oper

Statements of Consolidated Operations - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating revenue:
Passenger-Mainline	$ 26,552	$ 25,414	$ 26,333
Passenger-Regional	5,852	6,043	6,452
Total passenger revenue	32,404	31,457	32,785
Cargo	1,035	876	937
Other operating revenue	4,297	4,223	4,142
Total operating revenue	37,736	36,556	37,864
Operating expense:
Salaries and related costs	11,045	10,275	9,713
Aircraft fuel	6,913	5,813	7,522
Landing fees and other rent	2,240	2,165	2,203
Regional capacity purchase	2,232	2,197	2,290
Depreciation and amortization	2,149	1,977	1,819
Aircraft maintenance materials and outside repairs	1,856	1,749	1,651
Distribution expenses	1,349	1,303	1,342
Aircraft rent	621	680	754
Special charges (Note 14)	176	638	326
Other operating expenses	5,657	5,421	5,078
Total operating expenses	34,238	32,218	32,698
Operating income	3,498	4,338	5,166
Nonoperating income (expense):
Interest expense	(643)	(614)	(669)
Interest capitalized	84	72	49
Interest income	57	42	25
Miscellaneous, net (Note 14)	3	(19)	(352)
Total nonoperating expense, net	(499)	(519)	(947)
Income before income taxes	2,999	3,819	4,219
Income tax expense (benefit) (Note 14)	868	1,556	(3,121)
Net income	$ 2,131	$ 2,263	$ 7,340
Earnings per share, basic	$ 7.04	$ 6.86	$ 19.52
Earnings per share, diluted	$ 7.02	$ 6.85	$ 19.47
United Airlines, Inc.
Operating revenue:
Passenger-Mainline	$ 26,552	$ 25,414	$ 26,333
Passenger-Regional	5,852	6,043	6,452
Total passenger revenue	32,404	31,457	32,785
Cargo	1,035	876	937
Other operating revenue	4,297	4,223	4,142
Total operating revenue	37,736	36,556	37,864
Operating expense:
Salaries and related costs	11,045	10,275	9,713
Aircraft fuel	6,913	5,813	7,522
Landing fees and other rent	2,240	2,165	2,203
Regional capacity purchase	2,232	2,197	2,290
Depreciation and amortization	2,149	1,977	1,819
Aircraft maintenance materials and outside repairs	1,856	1,749	1,651
Distribution expenses	1,349	1,303	1,342
Aircraft rent	621	680	754
Special charges (Note 14)	176	638	326
Other operating expenses	5,655	5,418	5,076
Total operating expenses	34,236	32,215	32,696
Operating income	3,500	4,341	5,168
Nonoperating income (expense):
Interest expense	(643)	(614)	(670)
Interest capitalized	84	72	49
Interest income	57	42	25
Miscellaneous, net (Note 14)	3	(19)	(351)
Total nonoperating expense, net	(499)	(519)	(947)
Income before income taxes	3,001	3,822	4,221
Income tax expense (benefit) (Note 14)	852	1,558	(3,080)
Net income	$ 2,149	$ 2,264	$ 7,301

Statements of Consolidated Comp

Statements of Consolidated Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income	$ 2,131	$ 2,263	$ 7,340
Other comprehensive income (loss), net change related to:
Employee benefit plans, net of taxes	(195)	(313)	70
Fuel derivative financial instruments, net of taxes	1	316	182
Investments and other, net of taxes	(6)	(1)	(4)
Total other comprehensive income (loss), net	(200)	2	248
Total comprehensive income, net	1,931	2,265	7,588
United Airlines, Inc.
Net income	2,149	2,264	7,301
Other comprehensive income (loss), net change related to:
Employee benefit plans, net of taxes	(195)	(313)	70
Fuel derivative financial instruments, net of taxes	1	316	182
Investments and other, net of taxes	(6)	(1)	(4)
Total other comprehensive income (loss), net	(200)	2	248
Total comprehensive income, net	$ 1,949	$ 2,266	$ 7,549

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 1,482	$ 2,179
Short-term investments	2,316	2,249
Receivables, less allowance for doubtful accounts (2017-$7; 2016-$10)	1,340	1,176
Aircraft fuel, spare parts and supplies, less obsolescence allowance (2017-$354; 2016-$295)	924	873
Prepaid expenses and other	1,051	832
Total current assets	7,113	7,309
Operating property and equipment: Owned-
Flight equipment	28,692	25,873
Other property and equipment	6,946	5,652
Total owned property and equipment	35,638	31,525
Less-Accumulated depreciation and amortization	(11,159)	(9,975)
Total owned property and equipment, net	24,479	21,550
Purchase deposits for flight equipment	1,344	1,059
Capital leases-
Flight equipment	1,151	1,319
Other property and equipment	11	331
Total capital leases	1,162	1,650
Less-Accumulated amortization	(777)	(941)
Total capital leases, net	385	709
Total operating property and equipment, net	26,208	23,318
Other assets:
Goodwill	4,523	4,523
Intangibles, less accumulated amortization (2017-$1,313; 2016-$1,234)	3,539	3,632
Deferred income taxes		655
Restricted cash	91	124
Investments in affiliates and other, net	852	579
Total other assets	9,005	9,513
Total assets	42,326	40,140
Current liabilities:
Advance ticket sales	3,876	3,730
Frequent flyer deferred revenue	2,176	2,135
Accounts payable	2,196	2,139
Accrued salaries and benefits	2,166	2,307
Current maturities of long-term debt	1,565	849
Current maturities of capital leases	128	116
Other	569	1,010
Total current liabilities	12,676	12,286
Long-term debt	11,703	9,918
Long-term obligations under capital leases	996	822
Other liabilities and deferred credits:
Frequent flyer deferred revenue	2,565	2,748
Postretirement benefit liability	1,602	1,581
Pension liability	1,921	1,892
Advanced purchase of miles		430
Deferred income taxes	225
Lease fair value adjustment, net	198	277
Other	1,634	1,527
Total other liabilities and deferred credits	8,145	8,455
Commitments and contingencies
Stockholder's equity:
Preferred stock
Common stock	3	3
Additional capital invested	6,098	6,569
Retained earnings	4,621	3,427
Stock held in treasury, at cost	(769)	(511)
Accumulated other comprehensive loss	(1,147)	(829)
Total stockholder's equity	8,806	8,659
Total liabilities and stockholder's equity	42,326	40,140
United Airlines, Inc.
Current assets:
Cash and cash equivalents	1,476	2,173
Short-term investments	2,316	2,249
Receivables, less allowance for doubtful accounts (2017-$7; 2016-$10)	1,340	1,176
Aircraft fuel, spare parts and supplies, less obsolescence allowance (2017-$354; 2016-$295)	924	873
Prepaid expenses and other	1,051	832
Total current assets	7,107	7,303
Operating property and equipment: Owned-
Flight equipment	28,692	25,873
Other property and equipment	6,946	5,652
Total owned property and equipment	35,638	31,525
Less-Accumulated depreciation and amortization	(11,159)	(9,975)
Total owned property and equipment, net	24,479	21,550
Purchase deposits for flight equipment	1,344	1,059
Capital leases-
Flight equipment	1,151	1,319
Other property and equipment	11	331
Total capital leases	1,162	1,650
Less-Accumulated amortization	(777)	(941)
Total capital leases, net	385	709
Total operating property and equipment, net	26,208	23,318
Other assets:
Goodwill	4,523	4,523
Intangibles, less accumulated amortization (2017-$1,313; 2016-$1,234)	3,539	3,632
Deferred income taxes		612
Restricted cash	91	124
Investments in affiliates and other, net	852	579
Total other assets	9,005	9,470
Total assets	42,320	40,091
Current liabilities:
Advance ticket sales	3,876	3,730
Frequent flyer deferred revenue	2,176	2,135
Accounts payable	2,196	2,144
Accrued salaries and benefits	2,166	2,307
Current maturities of long-term debt	1,565	849
Current maturities of capital leases	128	116
Other	574	1,009
Total current liabilities	12,681	12,290
Long-term debt	11,703	9,918
Long-term obligations under capital leases	996	822
Other liabilities and deferred credits:
Frequent flyer deferred revenue	2,565	2,748
Postretirement benefit liability	1,602	1,581
Pension liability	1,921	1,892
Advanced purchase of miles		430
Deferred income taxes	252
Lease fair value adjustment, net	198	277
Other	1,634	1,527
Total other liabilities and deferred credits	8,172	8,455
Commitments and contingencies
Stockholder's equity:
Additional capital invested	1,787	3,573
Retained earnings	8,218	5,937
Accumulated other comprehensive loss	(1,147)	(829)
Receivable from related parties	(90)	(75)
Total stockholder's equity	8,768	8,606
Total liabilities and stockholder's equity	$ 42,320	$ 40,091

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Receivables, allowance for doubtful accounts	$ 7	$ 10
Aircraft fuel, spare parts and supplies, obsolescence allowance	354	295
Intangibles, accumulated amortization	$ 1,313	$ 1,234
Common stock, par value	$ 0.01	$ 0.01
Common shares, authorized	1,000,000,000	1,000,000,000
Common shares, outstanding	286,973,195	314,612,744
United Airlines, Inc.
Receivables, allowance for doubtful accounts	$ 7	$ 10
Aircraft fuel, spare parts and supplies, obsolescence allowance	354	295
Intangibles, accumulated amortization	$ 1,313	$ 1,234
Common stock, par value	$ 0.01	$ 0.01
Common shares, authorized	1,000	1,000
Common shares, issued	1,000	1,000
Common shares, outstanding	1,000	1,000

Statements of Consolidated Cash

Statements of Consolidated Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities:
Net income	$ 2,131	$ 2,263	$ 7,340
Adjustments to reconcile net income to net cash provided by operating activities -
Deferred income taxes	945	1,648	(3,177)
Depreciation and amortization	2,149	1,977	1,819
Special charges, non-cashportion	35	391	247
Other operating activities	142	109	115
Changes in operating assets and liabilities -
Decrease in fuel hedge collateral		26	551
Decrease in fuel derivatives		(20)	(305)
Decrease in other liabilities	(478)	(446)	(180)
Decrease in advanced purchase of miles	(865)	(249)	(224)
Increase (decrease) in frequent flyer deferred revenue	(142)	(60)	6
Increase in other assets	(533)	(298)	(160)
Increase (decrease) in accounts payable	66	239	(77)
Increase (decrease) in advance ticket sales	146	(22)	52
Increase in receivables	(183)	(16)	(15)
Net cash provided by operating activities	3,413	5,542	5,992
Investing Activities:
Capital expenditures	(3,998)	(3,223)	(2,747)
Purchases of short-term and other investments	(3,241)	(2,768)	(2,517)
Proceeds from sale of short-term and other investments	3,177	2,712	2,707
Proceeds from sale of property and equipment	12	28	86
Other, net	120	13	(136)
Net cash used in investing activities	(3,930)	(3,238)	(2,607)
Financing Activities:
Proceeds from issuance of long-term debt and airport construction financing	2,765	808	1,073
Repurchases of common stock	(1,844)	(2,614)	(1,233)
Payments of long-term debt	(901)	(1,215)	(2,178)
Principal payments under capital leases	(124)	(136)	(123)
Capitalized financing costs	(80)	(64)	(37)
Proceeds from the exercise of stock options	2	6	16
Other, net	(13)	2	(13)
Net cash used in financing activities	(195)	(3,213)	(2,495)
Net increase (decrease) in cash, cash equivalents and restricted cash	(712)	(909)	890
Cash, cash equivalents and restricted cash at beginning of year	2,303	3,212	2,322
Cash, cash equivalents and restricted cash at end of year	1,591	2,303	3,212
Investing and Financing Activities Not Affecting Cash:
Property and equipment acquired through the issuance of debt and capital leases	935	386	866
Equity interest in Republic Airways Holdings, Inc. received in consideration for bankruptcy claims	92
Airport construction financing	42	91	17
Operating lease conversions to capital lease		12	285
Exchange of convertible notes for common stock			202
Cash Paid During the Period for:
Interest	571	584	660
Income taxes	20	14	15
United Airlines, Inc.
Operating Activities:
Net income	2,149	2,264	7,301
Adjustments to reconcile net income to net cash provided by operating activities -
Deferred income taxes	929	1,650	(3,136)
Depreciation and amortization	2,149	1,977	1,819
Special charges, non-cashportion	35	391	247
Other operating activities	142	108	115
Changes in operating assets and liabilities -
Decrease in fuel hedge collateral		26	551
Decrease in fuel derivatives		(20)	(305)
Decrease in other liabilities	(479)	(444)	(181)
Decrease in advanced purchase of miles	(865)	(249)	(224)
Increase (decrease) in frequent flyer deferred revenue	(142)	(60)	6
Increase in other assets	(533)	(251)	(160)
Increase (decrease) in accounts payable	66	239	(77)
Increase (decrease) in advance ticket sales	146	(22)	52
Increase in receivables	(183)	(16)	(15)
Increase in intercompany receivables	(15)	(58)	(12)
Net cash provided by operating activities	3,399	5,535	5,981
Investing Activities:
Capital expenditures	(3,998)	(3,223)	(2,747)
Purchases of short-term and other investments	(3,241)	(2,768)	(2,517)
Proceeds from sale of short-term and other investments	3,177	2,712	2,707
Proceeds from sale of property and equipment	12	28	86
Other, net	120	13	(136)
Net cash used in investing activities	(3,930)	(3,238)	(2,607)
Financing Activities:
Proceeds from issuance of long-term debt and airport construction financing	2,765	808	1,073
Dividend to UAL	(1,844)	(2,614)	(1,233)
Payments of long-term debt	(901)	(1,215)	(2,178)
Principal payments under capital leases	(124)	(136)	(123)
Capitalized financing costs	(80)	(64)	(37)
Proceeds from the exercise of stock options	2	6	16
Other, net	1	9	(2)
Net cash used in financing activities	(181)	(3,206)	(2,484)
Net increase (decrease) in cash, cash equivalents and restricted cash	(712)	(909)	890
Cash, cash equivalents and restricted cash at beginning of year	2,297	3,206	2,316
Cash, cash equivalents and restricted cash at end of year	1,585	2,297	3,206
Investing and Financing Activities Not Affecting Cash:
Property and equipment acquired through the issuance of debt and capital leases	935	386	866
Equity interest in Republic Airways Holdings, Inc. received in consideration for bankruptcy claims	92
Airport construction financing	42	91	17
Operating lease conversions to capital lease		12	285
Cash Paid During the Period for:
Interest	571	584	660
Income taxes	$ 20	$ 14	$ 15

Statements of Consolidated Stoc

Statements of Consolidated Stockholder's Equity - USD ($) shares in Millions, $ in Millions	Total	United Airlines, Inc.	Common Stock	Additional Capital Invested	Additional Capital InvestedUnited Airlines, Inc.	Treasury Stock	Accumulated Deficit	Accumulated DeficitUnited Airlines, Inc.	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss)United Airlines, Inc.	Receivable from Related Parties, NetUnited Airlines, Inc.
Beginning Balance (in shares) at Dec. 31, 2014			375
Beginning Balance at Dec. 31, 2014	$ 2,396	$ 2,635	$ 4	$ 7,721	$ 7,347	$ (367)	$ (3,883)	$ (3,628)	$ (1,079)	$ (1,079)	$ (5)
Net income	7,340	7,301					7,340	7,301
Other comprehensive income (loss)	248	248							248	248
Convertible debt redemptions (in shares)			11
Convertible debt redemptions	202			202
Dividend to UAL		(1,232)			(1,232)
Share-based compensation	7	7		7	7
Proceeds from exercise of stock options	16			16
UAL contribution related to stock plans		16			16
Repurchases of common stock	(1,232)					(1,232)
Repurchases of common stock (in shares)			(21)
Other	(11)	(12)				(11)					(12)
Ending Balance (in shares) at Dec. 31, 2015			365
Ending Balance at Dec. 31, 2015	8,966	8,963	$ 4	7,946	6,138	(1,610)	3,457	3,673	(831)	(831)	(17)
Net income	2,263	2,264					2,263	2,264
Other comprehensive income (loss)	2	2							2	2
Dividend to UAL		(2,603)			(2,603)
Share-based compensation	32	32		32	32
Proceeds from exercise of stock options	6			6
UAL contribution related to stock plans		6			6
Repurchases of common stock	(2,607)					(2,607)
Repurchases of common stock (in shares)			(50)
Treasury stock retired			$ (1)	(1,415)		3,709	(2,293)
Other	(3)	(58)				(3)					(58)
Ending Balance (in shares) at Dec. 31, 2016			315
Ending Balance at Dec. 31, 2016	8,659	8,606	$ 3	6,569	3,573	(511)	3,427	5,937	(829)	(829)	(75)
Net income	2,131	2,149					2,131	2,149
Other comprehensive income (loss)	(200)	(200)							(200)	(200)
Dividend to UAL		(1,844)			(1,844)
Share-based compensation	56	56		56	56
Proceeds from exercise of stock options	2			2
UAL contribution related to stock plans		2			2
Repurchases of common stock	$ (1,844)					(1,844)
Repurchases of common stock (in shares)	(28)		(28)
Treasury stock retired				(508)		1,576	(1,068)
Net treasury stock issued for share-based awards	$ (12)			(21)		10	(1)
Excess tax benefits from share-based awards	14	14					14	14
Reclassification of stranded tax effects (Note 1)							118	118	(118)	(118)
Other		(15)									(15)
Ending Balance (in shares) at Dec. 31, 2017			287
Ending Balance at Dec. 31, 2017	$ 8,806	$ 8,768	$ 3	$ 6,098	$ 1,787	$ (769)	$ 4,621	$ 8,218	$ (1,147)	$ (1,147)	$ (90)

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Significant Accounting Policies	NOTE 1 - SIGNIFICANT ACCOUNTING POLICIES (a) Use of Estimates— (b) Revenue Recognition— Non-refundable Fees charged in association with changes or extensions to non-refundable non-refundable The Company records an estimate of breakage revenue on the flight date for tickets that will expire unused. These estimates are based on the evaluation of actual historical results and forecasted trends. Refundable tickets expire after one year from the date of issuance. The Company recognizes cargo and other revenue as service is provided. Under our capacity purchase agreements (“CPAs”) with regional carriers, we purchase all of the capacity related to aircraft covered by the contracts and are responsible for selling all of the related seat inventory. We record the passenger revenue and related expenses as separate operating revenue and expense in the consolidated statement of operations. Accounts receivable primarily consist of amounts due from credit card companies and customers of our aircraft maintenance and cargo transportation services. We provide an allowance for uncollectible accounts equal to the estimated losses expected to be incurred based on historical write-offs and other specific analyses. Bad debt expense and write-offs were not material for the years ended December 31, 2017, 2016 and 2015. (c) Frequent Flyer Accounting— non-airline non-travel Miles Earned in Conjunction with Flights When frequent flyers earn miles for flights, the Company recognizes a portion of the ticket sales as revenue when the air transportation occurs and defers a portion of the ticket sale representing the value of the related miles as a multiple-deliverable revenue arrangement. The Company determines the estimated selling price of air transportation and miles as if each element is sold on a separate basis. The total consideration from each ticket sale is then allocated to each of these elements, individually, on a pro rata basis. The miles are recorded in Frequent flyer deferred revenue on the Company’s consolidated balance sheet and recognized into revenue when the transportation is provided. The Company’s estimated selling price of miles is based on an equivalent ticket value less fulfillment discount, which incorporates the expected redemption of miles, as the best estimate of selling price for these miles. The equivalent ticket value is based on the prior 12 months’ weighted average equivalent ticket value of similar fares as those used to settle award redemptions while taking into consideration such factors as redemption pattern, cabin class, loyalty status and geographic region. The estimated selling price of miles is adjusted by a fulfillment discount that considers a number of factors, including redemption patterns of various customer groups. Co-branded United has a significant contract, the Second Amended and Restated Co-Branded “Co-Brand co-branded Co-Brand The fair value of the elements is determined using management’s estimated selling price of each element. The objective of using the estimated selling price based methodology is to determine the price at which we would transact a sale if the product or service were sold on a stand-alone basis. Accordingly, we determine our best estimate of selling price by considering multiple inputs and methods including, but not limited to, discounted cash flows, brand value, volume discounts, published selling prices, number of miles awarded and number of miles redeemed. The Company estimated the selling prices and volumes over the term of the Co-Brand The Company records passenger revenue related to the air transportation element when the transportation is delivered. The other elements are generally recognized as Other operating revenue when earned. Expiration of Miles The Company accounts for miles sold and awarded that will never be redeemed by program members, which we refer to as breakage. The Company reviews its breakage estimates annually based upon the latest available information regarding redemption and expiration patterns. Miles expire after 18 months of member account inactivity. The Company’s estimate of the expected expiration of miles requires significant management judgment. Current and future changes to expiration assumptions or to the expiration policy, or to program rules and program redemption opportunities, may result in material changes to the deferred revenue balance as well as recognized revenues from the programs. Other Information The following table provides additional information related to the frequent flyer program (in millions): Year Ended December 31, Cash Proceeds Other Revenue Recognized Upon Award of Miles Increase in Frequent Flyer Deferred Decrease in of Miles (c) 2017 $ 2,343 $ 1,183 $ 2,025 $ (865) 2016 3,022 1,221 2,050 (249) 2015 2,999 1,050 2,173 (224) (a) This amount represents other revenue recognized during the period from the sale of miles to third parties, representing the marketing-related deliverable services component of the sale. (b) This amount represents the increase to Frequent flyer deferred revenue during the period. (c) This amount represents the net decrease in the advance purchase of miles obligation due to cash payments for the sale of miles less than miles awarded to customers. (d) Cash and Cash Equivalents and Restricted Cash— Restricted cash primarily includes cash collateral for letters of credit and collateral associated with obligations for facility leases and workers’ compensation. Restricted cash is classified as short-term or long-term in the consolidated balance sheets based on the expected timing of return of the assets to the Company. The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the consolidated balance sheets that sum to the total of the same such amounts shown in the statements of consolidated cash flows: UAL United At December 31, At December 31, 2017 2016 2015 2017 2016 2015 Current assets: Cash and cash equivalents $ 1,482 $ 2,179 $ 3,006 $ 1,476 $ 2,173 $ 3,000 Restricted cash included in Prepaid expenses and other 18 — 2 18 — 2 Other assets: Restricted cash 91 124 204 91 124 204 Total cash, cash equivalents and restricted cash shown in the statement of consolidated cash flows $ 1,591 $ 2,303 $ 3,212 $ 1,585 $ 2,297 $ 3,206 (e) Short-term Investments— available-for-sale available-for-sale (f) Aircraft Fuel, Spare Parts and Supplies— (g) Property and Equipment— Depreciation and amortization of owned depreciable assets is based on the straight-line method over the assets’ estimated useful lives. Leasehold improvements are amortized over the remaining term of the lease, including estimated facility renewal options when renewal is reasonably assured at key airports, or the estimated useful life of the related asset, whichever is less. Properties under capital leases are amortized on the straight-line method over the life of the lease or, in the case of certain aircraft, over their estimated useful lives, whichever is shorter. Amortization of capital lease assets is included in depreciation and amortization expense. The estimated useful lives of property and equipment are as follows: Estimated Useful Life (in years) Aircraft and related rotable parts 25 to 30 Buildings 25 to 45 Other property and equipment 3 to 15 Computer software 5 to 15 Building improvements 1 to 40 As of December 31, 2017 and 2016, the Company had a carrying value of computer software of $345 million and $356 million, respectively. For the years ended December 31, 2017, 2016 and 2015, the Company’s depreciation expense related to computer software was $117 million, $108 million and $93 million, respectively. Aircraft and aircraft spare parts were assumed to have residual values of approximately 10% of original cost, and other categories of property and equipment were assumed to have no residual value. (h) Maintenance and Repairs— power-by-the-hour (i) Lease Fair Value Adjustments— (j) Regional Capacity Purchase— (k) Advertising— (l) Intangibles— (m) Long-Lived Asset Impairments— (n) Share-Based Compensation— (o) Ticket Taxes— (p) Retirement of Leased Aircraft— (q) Uncertain Income Tax Positions— (r) Labor Costs— (s) Third-Party Business— non-air non-air (t) Recently Issued Accounting Standards— Revenue from Contracts with Customers . Revenue Recognition Statements of Consolidated Operations for the Years Ended December 31, As Reported Adjustment As Adjusted for Adoption of 2017 2016 2017 2016 2017 2016 Operating revenue: Passenger—Mainline $ 26,552 $ 25,414 $ 1,707 $ 1,615 $ 28,259 $ 27,029 Passenger—Regional 5,852 6,043 349 357 6,201 6,400 Total passenger revenue 32,404 31,457 2,056 1,972 34,460 33,429 Cargo 1,035 876 79 58 1,114 934 Other operating revenue 4,297 4,223 (2,087) (2,028) 2,210 2,195 Total operating revenue 37,736 36,556 48 2 37,784 36,558 Operating expenses 34,238 32,218 (21) (12) 34,217 32,206 Operating income 3,498 4,338 69 14 3,567 4,352 Nonoperating expense, net (499) (519) (28) (60) (527) (579) Income before income taxes 2,999 3,819 41 (46) 3,040 3,773 Income tax expense (benefit) 868 1,556 28 (17) 896 1,539 Net income $ 2,131 $ 2,263 $ 13 $ (29) $ 2,144 $ 2,234 Earnings per share, basic $ 7.04 $ 6.86 $ 0.04 $ (0.09) $ 7.08 $ 6.77 Earnings per share, diluted $ 7.02 $ 6.85 $ 0.04 $ (0.09) $ 7.06 $ 6.76 Consolidated Balance Sheets as of December 31, As Reported Adjustment As Adjusted for Adoption of 2017 2016 2017 2016 2017 2016 Current assets: Prepaid expenses and other $ 1,051 $ 832 $ 20 $ 20 $ 1,071 $ 852 Other assets: Deferred income taxes — 655 — 48 — 703 Current liabilities: Advance ticket sales 3,876 3,730 64 65 3,940 3,795 Frequent flyer deferred revenue 2,176 2,135 16 14 2,192 2,149 Other 569 1,010 7 79 576 1,089 Other liabilities and deferred credits: Frequent flyer deferred revenue 2,565 2,748 26 (8 ) 2,591 2,740 Advanced purchase of miles — 430 — 3 — 433 Deferred income taxes 225 — (21) — 204 — Stockholders’ equity: Retained earnings 4,621 3,427 (72) (85 ) 4,549 3,342 In 2016, the FASB amended the FASB Accounting Standards Codification and created a new Topic 842, Leases right-of-use Leases In 2016, the FASB issued Accounting Standards Update No. 2016-01, Financial Instruments—Overall 825-10) 2016-01”). available-for-sale 2016-01 In 2017, the FASB issued Accounting Standards Update No. 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost 2017-07”). . 2017-07 2017-07 2017-07 Statements of Consolidated Operations for the Years Ended December 31, As Reported Adjustment As Adjusted for Adoption of ASU 2017-07 2017 2016 2017 2016 2017 2016 Operating expense: Salaries and related costs $ 11,045 $ 10,275 $ (104) $ (99 ) $ 10,941 $ 10,176 Special charges 176 638 — 107 176 745 Nonoperating income (expense): Miscellaneous, net 3 (19) (104) 8 (101) (11) In February 2018, the FASB issued Accounting Standards Update No. 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income 2018-02”). 2018-02

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill and Other Intangible Assets	NOTE 2 - GOODWILL AND OTHER INTANGIBLE ASSETS The following table presents information about the Company’s goodwill and other intangible assets at December 31 (in millions): 2017 2016 Item Asset life (a) Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Goodwill $ 4,523 $ 4,523 Finite-lived intangible assets Frequent flyer database (b) 22 $ 1,177 $ 832 $ 1,177 $ 771 Hubs 20 145 89 145 82 Contracts 13 121 103 135 95 Patents and tradenames 3 108 108 108 108 Airport slots and gates 8 97 97 97 97 Other 25 109 84 109 81 Total $ 1,757 $ 1,313 $ 1,771 $ 1,234 Indefinite-lived intangible assets Route authorities $ 1,562 $ 1,562 Airport slots and gates 536 536 Tradenames and logos 593 593 Alliances 404 404 Total $ 3,095 $ 3,095 (a) Weighted average life expressed in years. (b) The frequent flyer database is amortized based on an accelerated amortization schedule to reflect utilization of the assets. Estimated cash flows correlating to the expected attrition rate of customers in the frequent flyer database is considered in the determination of the amortization schedules. Amortization expense in 2017, 2016 and 2015 was $79 million, $90 million and $105 million, respectively. Projected amortization expense in 2018, 2019, 2020, 2021 and 2022 is $67 million, $61 million, $55 million, $50 million and $40 million, respectively. See Note 14 of this report for additional information related to impairment of intangible assets.

Common Stockholders' Equity and

Common Stockholders' Equity and Preferred Securities	12 Months Ended
	Dec. 31, 2017
Common Stockholders' Equity and Preferred Securities	NOTE 3 – COMMON STOCKHOLDERS’ EQUITY AND PREFERRED SECURITIES In 2017, UAL repurchased approximately 28 million shares of UAL common stock for $1.8 billion, completing its July 2016 repurchase authorization. In December 2017, UAL’s Board of Directors authorized a new $3.0 billion share repurchase program to acquire UAL’s common stock. As of December 31, 2017, the Company had approximately $3.0 billion remaining to purchase shares under its existing share repurchase authority. UAL may repurchase shares through the open market, privately negotiated transactions, block trades or accelerated share repurchase transactions from time to time in accordance with applicable securities laws. UAL may repurchase shares of UAL common stock subject to prevailing market conditions, and may discontinue such repurchases at any time. See Part II, Item 5, Market for registrant’s common equity, related stockholder matters and issuer purchases of equity securities, of this report for additional information. In 2017, the Company retired 25 million treasury shares that were originally acquired at an average cost of approximately $63 per share. At December 31, 2017, approximately 10 million shares of UAL’s common stock were reserved for future issuance related to the issuance of equity-based awards under the Company’s incentive compensation plans. As of December 31, 2017, UAL had two shares of junior preferred stock (par value $0.01 per share) outstanding. In addition, UAL is authorized to issue 250 million shares of preferred stock (without par value) under UAL’s amended and restated certificate of incorporation.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share	NOTE 4 - EARNINGS PER SHARE The computations of UAL’s basic and diluted earnings per share are set forth below for the years ended December 31 (in millions, except per share amounts): 2017 2016 2015 Earnings available to common stockholders $ 2,131 $ 2,263 $ 7,340 Basic weighted-average shares outstanding 302.7 329.9 376.1 Effect of convertible notes — — 0.3 Effect of employee stock awards 0.9 0.4 0.5 Diluted weighted-average shares outstanding 303.6 330.3 376.9 Earnings per share, basic $ 7.04 $ 6.86 $ 19.52 Earnings per share, diluted $ 7.02 $ 6.85 $ 19.47 The number of antidilutive securities excluded from the computation of diluted earnings per share amounts was not material.

Share-Based Compensation Plans

Share-Based Compensation Plans	12 Months Ended
	Dec. 31, 2017
Share-Based Compensation Plans	NOTE 5 - SHARE-BASED COMPENSATION PLANS UAL maintains several share-based compensation plans. In May 2017, UAL’s Board of Directors and stockholders approved the United Continental Holdings, Inc. 2017 Incentive Compensation Plan (the “2017 Plan”). The 2017 Plan is an incentive compensation plan that allows the Company to use different forms of long-term equity incentives to attract, retain, and reward officers and employees (including prospective officers and employees). The 2017 Plan replaced the United Continental Holdings, Inc. 2008 Incentive Compensation Plan (the “2008 Plan”). Any awards granted under the 2008 Plan prior to the approval of the 2017 Plan remain in effect pursuant to their terms. Awards may not be granted under the 2017 Plan after May 24, 2027. Under the 2017 Plan, the Company may grant: non-qualified All awards are recorded as either equity or a liability in the Company’s consolidated balance sheets. The share-based compensation expense is recorded in salaries and related costs. During 2017, UAL granted share-based compensation awards pursuant to both the 2008 Plan and the 2017 Plan. These share-based compensation awards include approximately 1.6 million RSUs, consisting of 1.0 million time-vested RSUs and 0.6 million performance-based RSUs, and approximately 36,000 stock options. The time-vested RSUs vest pro-rata, 20-day pre-tax 20-day ten-year pro-rata The following table provides information related to UAL’s share-based compensation plan cost for the years ended December 31 (in millions): 2017 2016 2015 Compensation cost: RSUs $ 63 $ 58 $ 52 Restricted stock 8 11 6 Stock options 2 1 — Total $ 73 $ 70 $ 58 The table below summarizes UAL’s unearned compensation and weighted-average remaining period to recognize costs for all outstanding share-based awards that are probable of being achieved as of December 31, 2017 (in millions, except as noted): Unearned Weighted- Average Remaining (in years) RSUs $ 46 1.9 Stock options 4 3.9 Restricted stock 3 1.2 Total $ 53 RSUs and Restricted Stock The table below summarizes UAL’s RSUs and restricted stock activity for the years ended December 31 (shares in millions): RSUs Restricted Stock Weighted- Outstanding at December 31, 2014 3.8 0.7 $ 32.55 Granted 1.0 0.2 66.53 Vested (1.6) (0.4) 31.14 Forfeited (0.6) (0.2) 46.23 Outstanding at December 31, 2015 2.6 0.3 48.68 Granted 1.9 0.4 50.63 Vested (1.4) (0.1) 41.47 Forfeited (0.2) (0.1) 53.42 Outstanding at December 31, 2016 2.9 0.5 52.00 Granted 1.6 — — Vested (1.0) (0.2) 51.60 Forfeited (0.3) — 51.88 Outstanding at December 31, 2017 3.2 0.3 52.30 The fair value of RSUs and restricted stock that vested in 2017, 2016 and 2015 was $76 million, $80 million and $92 million, respectively. The fair value of the restricted stock and the stock-settled RSUs was based upon the UAL common stock price on the date of grant. These awards are accounted for as equity awards. The fair value of the cash-settled RSUs was based on the UAL common stock price as of the last day preceding the settlement date. These awards are accounted for as liability awards. Restricted stock vesting and the recognition of the expense is similar to the stock option vesting described below. Stock Options The Company determined the grant date fair value of stock options using a Black Scholes option pricing model, which requires the use of several assumptions. The risk-free interest rate is based on the U.S. treasury yield curve in effect for the expected term of the option at the time of grant. The dividend yield on UAL’s common stock was assumed to be zero since UAL did not have any plans to pay dividends at the time of the option grants. The volatility assumptions were based upon historical volatilities of UAL using daily stock price returns equivalent to the expected term of the option. The expected term of the options was determined based upon a simplified assumption that the option will be exercised evenly from vesting to expiration due to the Company’s lack of relevant historical data related to stock options. As of December 31, 2017, there were approximately 0.5 million outstanding stock option awards, 0.1 million of which were exercisable, with weighted-average exercise prices of $51.67 and $34.74, respectively, intrinsic values of $8 million and $5 million, respectively, and weighted-average remaining contractual lives (in years) of 6.3 and 3.7, respectively.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss)	NOTE 6 - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) The tables below present the components of the Company’s AOCI, net of tax (in millions): Pension and Other Postretirement Liabilities Fuel Investments Deferred Total Balance at December 31, 2014 $ (472) $ (499) $ 8 $ (116) $ (1,079) Other comprehensive income (loss) before reclassifications 78 (a) (320) (5) 88 (159) Amounts reclassified from accumulated other comprehensive income 31 604 — (228) 407 Net other comprehensive income (loss) 109 284 (5) (140) 248 Balance at December 31, 2015 $ (363) $ (215) $ 3 $ (256) $ (831) Other comprehensive income (loss) before reclassifications (517) (a) (4) — 187 (334) Amounts reclassified from accumulated other comprehensive income 26 217 (2) 95 336 Net other comprehensive income (loss) (491) 213 (2) 282 2 Balance at December 31, 2016 $ (854) $ (2) $ 1 $ 26 $ (829) Other comprehensive income (loss) before reclassifications (306) (a) — (7) 74 (239) Amounts reclassified from accumulated other comprehensive income 58 2 — (21) 39 Reclassification of stranded tax effects — — — (118) (b) (118) Net other comprehensive income (loss) (248) 2 (7) (65) (318) Balance at December 31, 2017 $ (1,102) $ — $ (6) $ (39) (c) $ (1,147) Details about AOCI Components Amount Reclassified from AOCI to Affected Line Item in Year Ended December 31, 2017 2016 2015 Fuel derivative contracts Fuel contracts-reclassifications of losses into earnings (d) $ 2 $ 217 $ 604 Aircraft fuel Pension and Postretirement liabilities Amortization of unrecognized (gains) losses and prior service cost (e) 58 26 31 Salaries and related costs Investments and other Available-for-sale — (2 ) — Miscellaneous, net (a) Prior service credits increased by $0 million, $30 million and $0 million and actuarial losses increased by approximately $306 million, $560 million and $78 million for 2017, 2016 and 2015, respectively. (b) This amount represents the reclassification from AOCI to RE of the stranded tax effects resulting from the enactment of the Tax Act. (c) Deferred tax balance relates mainly to Pension and Other Postretirement Liabilities. (d) The last of the Company’s fuel hedge derivatives designated for cash flow hedge accounting expired in December 2016. The 2017 amount reclassified from AOCI into fuel expense represents hedge losses on December 2016 settled trades, but for which the associated fuel purchased in December 2016 was not consumed until January 2017. The Company’s current strategy is to not enter into transactions to hedge its fuel consumption, although the Company regularly reviews its strategy based on market conditions and other factors. (e) This AOCI component is included in the computation of net periodic pension and other postretirement costs (see Note 8 of this report for additional information). Prior to the release of the deferred income tax valuation allowance in the third quarter of 2015, the Company recorded approximately $465 million of valuation allowance adjustments in AOCI. Subsequent to the release of the deferred income tax valuation allowance in 2015, the $465 million debit remained within AOCI, of which $180 million related to losses on fuel hedges designated for hedge accounting and $285 million related to pension and other postretirement liabilities. Accounting rules required the adjustments to remain in AOCI as long as the Company had fuel derivatives designated for cash flow hedge accounting and the Company continues to provide pension and postretirement benefits. In 2016, the Company settled all of its fuel hedges and has not entered into any new fuel derivative contracts for hedge accounting. Accordingly, the Company reclassified the $180 million to income tax expense in 2016.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Taxes	NOTE 7 - INCOME TAXES The income tax provision (benefit) differed from amounts computed at the statutory federal income tax rate and consisted of the following significant components, as follows (in millions): UAL 2017 2016 2015 Income tax provision at statutory rate $ 1,050 $ 1,337 $ 1,477 State income taxes, net of federal income tax benefit 29 38 38 Foreign tax rate differential (43) — — Foreign income taxes 3 3 4 Nondeductible employee meals 17 16 15 Impact of Tax Act (192) — — Income tax adjustment from AOCI — 180 — State rate change 12 (12) — Valuation allowance (16) 20 (4,662) Other, net 8 (26) 7 $ 868 $ 1,556 $ (3,121) Current $ (77) $ (92) $ 56 Deferred 945 1,648 (3,177) $ 868 $ 1,556 $ (3,121) United 2017 2016 2015 Income tax provision at statutory rate $ 1,051 $ 1,338 $ 1,477 State income taxes, net of federal income tax 29 38 38 Foreign tax rate differential (43) — — Foreign income taxes 3 3 4 Nondeductible employee meals 17 16 15 Impact of Tax Act (209) — — Income tax adjustment from AOCI — 180 — State rate change 12 (12) — Valuation allowance (16) 20 (4,621) Other, net 8 (25) 7 $ 852 $ 1,558 $ (3,080) Current $ (77) $ (92) $ 56 Deferred 929 1,650 (3,136) $ 852 $ 1,558 $ (3,080) The Company’s effective tax rate for the year ended December 31, 2017 differed from the federal statutory rate of 35% primarily because of the provisional one-time non-deductible one-time non-cash Total income tax expense in 2017 includes the provisional one-time one-time As of December 31, 2017, we had not completed our analysis of all aspects of the Tax Act. However, we have made a provisional estimate for its effect on our existing deferred tax balances and the one-time Temporary differences and carryforwards that give rise to deferred tax assets and liabilities at December 31, 2017 and 2016 were as follows (in millions): UAL United 2017 2016 2017 2016 Deferred income tax asset (liability): Federal and state net operating loss (“NOL”) carryforwards $ 601 $ 1,613 $ 574 $ 1,571 Deferred revenue 1,069 2,096 1,069 2,096 Employee benefits, including pension, postretirement and medical 1,051 1,662 1,051 1,662 Alternative minimum tax credit carryforwards — 116 — 116 Other 351 523 351 522 Less: Valuation allowance (63) (68) (63) (68) Total deferred tax assets $ 3,009 $ 5,942 $ 2,982 $ 5,899 Depreciation $ (2,431) $ (3,961) $ (2,431) $ (3,961) Intangibles (803) (1,326) (803) (1,326) Total deferred tax liabilities $ (3,234) $ (5,287) $ (3,234) $ (5,287) Net deferred tax asset (liability) $ (225) $ 655 $ (252) $ 612 United and its domestic consolidated subsidiaries file a consolidated federal income tax return with UAL. Under an intercompany tax allocation policy, United and its subsidiaries compute, record and pay UAL for their own tax liability as if they were separate companies filing separate returns. In determining their own tax liabilities, United and each of its subsidiaries take into account all tax credits or benefits generated and utilized as separate companies and they are each compensated for the aforementioned tax benefits only if they would be able to use those benefits on a separate company basis. The Company’s federal and state NOL carryforwards relate to prior years’ NOLs, which may be used to reduce tax liabilities in future years. These tax benefits are mostly attributable to federal pre-tax pre-tax 20-year The Company periodically assesses whether it is more likely than not that it will generate sufficient taxable income to realize its deferred income tax assets. The Company establishes valuation allowances if it is not more likely than not that it will realize its deferred income tax assets. In making this determination, the Company considers all available positive and negative evidence and makes certain assumptions. The Company considers, among other things, projected future taxable income, scheduled reversals of deferred tax liabilities, the overall business environment, the Company’s historical financial results and tax planning strategies. In evaluating the likelihood of utilizing the Company’s net deferred income tax assets, the significant factors that the Company considers include (1) the Company’s recent history and forecasted profitability; (2) growth in the U.S. and global economies; and (3) the future impact of taxable temporary differences. In 2015, the Company concluded that its deferred income tax assets were more likely than not to be realized and released almost all of its valuation allowance in 2015, resulting in a $3.1 billion benefit in its provision for income taxes. The Company has a valuation allowance of $63 million for certain state and local NOLs and credit carryforwards. The Company expects these NOLs and credits will expire unused due to limited carryforward periods. The ability to utilize these state NOLs and credits will be evaluated on a quarterly basis to determine if there are any significant events or any prudent and feasible tax planning strategies that would affect the Company’s ability to realize these deferred tax assets. The Company’s unrecognized tax benefits related to uncertain tax positions were $21 million, $74 million and $24 million at December 31, 2017, 2016 and 2015, respectively. Included in the ending balance at December 31, 2017 is $21 million that would affect the Company’s effective tax rate if recognized. The changes in unrecognized tax benefits relating to settlements with taxing authorities, unrecognized tax benefits as a result of tax positions taken during a prior period and unrecognized tax benefits relating from a lapse of the statute of limitations were immaterial during 2017, 2016 and 2015. The Company does not expect significant increases or decreases in their unrecognized tax benefits within the next 12 months. There are no material amounts included in the balance at December 31, 2017 for tax positions for which the ultimate deductibility is highly certain but for which there is uncertainty about the timing of such deductibility. The Company’s federal income tax returns for tax years after 2001 remain subject to examination by the Internal Revenue Service (“IRS”) and state taxing jurisdictions. Currently, there are no ongoing examinations of the Company’s prior year tax returns being conducted by the IRS.

Pension and Other Postretiremen

Pension and Other Postretirement Plans	12 Months Ended
	Dec. 31, 2017
Pension and Other Postretirement Plans	NOTE 8 - PENSION AND OTHER POSTRETIREMENT PLANS The following summarizes the significant pension and other postretirement plans of United: Pension Plans United maintains two primary defined benefit pension plans, one covering certain pilot employees and another covering certain U.S. non-pilot non-pilot Other Postretirement Plans United maintains postretirement medical programs which provide medical benefits to certain retirees and eligible dependents, as well as life insurance benefits to certain retirees participating in the plan. Benefits provided are subject to applicable contributions, co-payments, Actuarial assumption changes are reflected as a component of the net actuarial gains/(losses) during 2017 and 2016. These amounts will be amortized over the average remaining service life of the covered active employees or the average life expectancy of inactive participants and will impact 2017 and 2016 pension and retiree medical expense as described below. The following table sets forth the reconciliation of the beginning and ending balances of the benefit obligation and plan assets, the funded status and the amounts recognized in these financial statements for the defined benefit and other postretirement plans (in millions): Pension Benefits Year Ended Year Ended Accumulated benefit obligation: $ 4,739 $ 4,158 Change in projected benefit obligation: Projected benefit obligation at beginning of year $ 5,253 $ 4,473 Service cost 195 112 Interest cost 220 200 Actuarial loss 525 738 Gross benefits paid and settlements (366) (243) Other 25 (27) Projected benefit obligation at end of year $ 5,852 $ 5,253 Change in plan assets: Fair value of plan assets at beginning of year $ 3,355 $ 2,975 Actual return on plan assets 510 230 Employer contributions 419 421 Gross benefits paid and settlements (366) (243) Other 14 (28) Fair value of plan assets at end of year $ 3,932 $ 3,355 Funded status—Net amount recognized $ (1,920) $ (1,898) Pension Benefits December 31, 2017 December 31, 2016 Amounts recognized in the consolidated balance sheets consist of: Noncurrent asset $ 9 $ 2 Current liability (8) (8) Noncurrent liability (1,921) (1,892) Total liability $ (1,920) $ (1,898) Amounts recognized in accumulated other comprehensive loss consist of: Net actuarial loss $ (1,610) $ (1,482) Prior service cost (1) (1) Total accumulated other comprehensive loss $ (1,611) $ (1,483) Other Postretirement Benefits Year Ended Year Ended Change in benefit obligation: Benefit obligation at beginning of year $ 1,687 $ 2,002 Service cost 13 19 Interest cost 66 86 Plan participants’ contributions 68 69 Benefits paid (178) (191) Actuarial loss (gain) 40 (165) Plan amendments — (138) Other 14 5 Benefit obligation at end of year $ 1,710 $ 1,687 Change in plan assets: Fair value of plan assets at beginning of year $ 55 $ 56 Actual return on plan assets 1 2 Employer contributions 108 119 Plan participants’ contributions 68 69 Benefits paid (178) (191) Fair value of plan assets at end of year 54 55 Funded status—Net amount recognized $ (1,656) $ (1,632) Other Postretirement Benefits December 31, 2017 December 31, 2016 Amounts recognized in the consolidated balance sheets consist of: Current liability $ (54) $ (51) Noncurrent liability (1,602) (1,581) Total liability $ (1,656) $ (1,632) Amounts recognized in accumulated other comprehensive income consist of: Net actuarial gain $ 301 $ 384 Prior service credit 208 245 Total accumulated other comprehensive income $ 509 $ 629 The following information relates to all pension plans with an accumulated benefit obligation and a projected benefit obligation in excess of plan assets at December 31 (in millions): 2017 2016 Projected benefit obligation $ 5,637 $ 5,025 Accumulated benefit obligation 4,567 3,985 Fair value of plan assets 3,709 3,164 Net periodic benefit cost for the years ended December 31 included the following components (in millions): 2017 2016 2015 Pension Other Pension Other Pension Other Service cost $ 195 $ 13 $ 112 $ 19 $ 124 $ 21 Interest cost 220 66 200 86 200 82 Expected return on plan assets (243) (2) (216) (2) (194) (2) Curtailment gain — — — (107) — — Amortization of unrecognized actuarial (gain) loss 128 (33) 76 (19) 85 (22) Amortization of prior service credits — (37) — (31) — (32) Other 5 — 5 — 4 — Net periodic benefit cost (credit) $ 305 $ 7 $ 177 $ (54) $ 219 $ 47 See Note 14 of this report for additional information related to the curtailment gain recorded in 2016. The estimated amounts that will be amortized in 2018 out of accumulated other comprehensive income (loss) into net periodic benefit cost are as follows (in millions): Pension Benefits Other Actuarial (gain) loss $ 132 $ (32) Prior service (credit) cost — (37) The assumptions used for the benefit plans were as follows: Pension Benefits Assumptions used to determine benefit obligations 2017 2016 Discount rate 3.65% 4.18% Rate of compensation increase 3.89% 3.54% Assumptions used to determine net expense Discount rate 4.19% 4.58% Expected return on plan assets 7.02% 7.04% Rate of compensation increase 3.54% 3.53% Other Postretirement Benefits Assumptions used to determine benefit obligations 2017 2016 Discount rate 3.63% 4.07% Assumptions used to determine net expense Discount rate 4.07% 4.49% Expected return on plan assets 3.00% 3.00% Health care cost trend rate assumed for next year 6.25% 6.50% Rate to which the cost trend rate is assumed to decline (ultimate trend rate in 2023) 5.00% 5.00% The Company used the Society of Actuaries’ 2014 mortality tables, modified to reflect the Social Security Administration Trustee’s Report on current projections regarding expected longevity improvements. The Company selected the 2017 discount rate for substantially all of its plans by using a hypothetical portfolio of high quality bonds at December 31, 2017, that would provide the necessary cash flows to match projected benefit payments. We develop our expected long-term rate of return assumption for our defined benefit plans based on historical experience and by evaluating input from the trustee managing the plans’ assets. Our expected long-term rate of return on plan assets for these plans is based on a target allocation of assets, which is based on our goal of earning the highest rate of return while maintaining risk at acceptable levels. The plans strive to have assets sufficiently diversified so that adverse or unexpected results from one security class will not have an unduly detrimental impact on the entire portfolio. Plan fiduciaries regularly review our actual asset allocation and the pension plans’ investments are periodically rebalanced to our targeted allocation when considered appropriate. United’s plan assets are allocated within the following guidelines: Percent of Total Expected Long-Term Rate of Return Equity securities 27-42 % 9.5 % Fixed-income securities 30-40 5.5 Alternatives 10-25 7.3 Other 0-10 7.3 One-hundred Assumed health care cost trend rates have a significant effect on the amounts reported for the other postretirement plans. A 1% change in the assumed health care trend rate for the Company would have the following additional effects (in millions): 1% Increase 1% Decrease Effect on total service and interest cost for the year ended December 31, 2017 $ 11 $ (8) Effect on postretirement benefit obligation at December 31, 2017 170 (149) A one percentage point decrease in the weighted average discount rate would increase the Company’s postretirement benefit liability by approximately $185 million and increase the estimated 2017 benefits expense by approximately $8 million. Fair Value Information. Level 1 Unadjusted quoted prices in active markets for assets or liabilities identical to those to be reported at fair value Level 2 Other inputs that are observable directly or indirectly, such as quoted prices for similar assets or liabilities or market-corroborated inputs Level 3 Unobservable inputs for which there is little or no market data and which require us to develop our own assumptions about how market participants would price the assets or liabilities Assets and liabilities measured at fair value are based on the valuation techniques identified in the tables below. The valuation techniques are as follows: (a) Market approach. (b) Income approach. The following tables present information about United’s pension and other postretirement plan assets at December 31 (in millions): 2017 2016 Pension Plan Assets: Total Level 1 Level 2 Level 3 Assets Total Level 1 Level 2 Level 3 Assets Equity securities funds $ 1,406 $ 269 $ 133 $ — $ 1,004 $ 1,173 $ 230 $ 111 $ — $ 832 Fixed-income securities 1,470 — 834 18 618 1,298 — 824 11 463 Alternatives 637 — — 139 498 586 — — 134 452 Other investments 419 32 124 172 91 298 47 68 87 96 Total $ 3,932 $ 301 $ 1,091 $ 329 $ 2,211 $ 3,355 $ 277 $ 1,003 $ 232 $ 1,843 Other Postretirement Benefit Plan Assets: Deposit administration fund $ 54 $ — $ — $ 54 $ — $ 55 $ — $ — $ 55 $ — (a) In accordance with the relevant accounting standards, certain investments that are measured at fair value using the net asset value (“NAV”) per share (or its equivalent) have not been classified in the fair value hierarchy. These investments are commingled funds that invest in fixed-income instruments including bonds, debt securities, and other similar instruments issued by various U.S. and non-U.S. Equity and Fixed-Income. non-U.S. non-U.S Deposit Administration Fund. Alternatives. Other investments. The reconciliation of United’s defined benefit plan assets measured at fair value using unobservable inputs (Level 3) for the years ended December 31, 2017 and 2016 is as follows (in millions): 2017 2016 Balance at beginning of year $ 287 $ 208 Actual return on plan assets: Sold during the year 7 4 Held at year end 16 3 Purchases, sales, issuances and settlements (net) 73 72 Balance at end of year $ 383 $ 287 Funding requirements for tax-qualified The estimated future benefit payments, net of expected participant contributions, in United’s pension plans and other postretirement benefit plans as of December 31, 2017 are as follows (in millions): Pension Other Postretirement Other Postretirement— subsidy receipts 2018 $ 305 $ 113 $ 6 2019 326 118 6 2020 331 121 6 2021 357 124 7 2022 369 126 7 Years 2023 – 2027 1,912 646 43 Defined Contribution Plans Depending upon the employee group, employer contributions consist of matching contributions and/or non-elective Multi-Employer Plans United’s participation in the IAM National Pension Plan (“IAM Plan”) for the annual period ended December 31, 2017 is outlined in the table below. There have been no significant changes that affect the comparability of 2017 and 2016 contributions. The risks of participating in these multi-employer plans are different from single-employer plans, as United may be subject to additional risks that others do not meet their obligations, which in certain circumstances could revert to United. The IAM Plan reported $414 million in employers’ contributions for the year ended December 31, 2016. For 2016, the Company’s contributions to the IAM Plan represented more than 5% of total contributions to the IAM Plan. Pension Fund IAM National Pension Fund EIN/ Pension Plan Number 51-6031295 - 002 Pension Protection Act Zone Status (2017 and 2016) Green Zone. Plans in the green zone are at least 80 percent funded. FIP/RP Status Pending/Implemented No United’s Contributions $50 million, $41 million and $40 million in the years ended December 31, 2017, 2016 and 2015, respectively Surcharge Imposed No Expiration Date of Collective Bargaining Agreement N/A At the date the Consolidated Financial Statements were issued, Forms 5500 were not available for the plan year ending in 2017. Profit Sharing Substantially all employees participate in profit sharing based on a percentage of pre-tax pre-tax co-workers co-worker’s co-workers non-U.S. co-workers

Fair Value Measurements and Inv

Fair Value Measurements and Investments	12 Months Ended
	Dec. 31, 2017
Fair Value Measurements and Investments	NOTE 9 - FAIR VALUE MEASUREMENTS AND INVESTMENTS Fair Value Information. 2017 2016 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Cash and cash equivalents $ 1,482 $ 1,482 $ — $ — $ 2,179 $ 2,179 $ — $ — Short-term investments: Corporate debt 958 — 958 — 835 — 835 — Asset-backed securities 753 — 753 — 792 — 792 — Certificates of deposit placed through an account registry service (“CDARS”) 120 — 120 — 246 — 246 — U.S. government and agency notes 113 — 113 — 140 — 140 — Other fixed-income securities 188 — 188 — 54 — 54 — Other investments measured at NAV 184 — — — 182 — — — Restricted cash 109 109 — — 124 124 — — Long-term investments: Equity securities 99 99 — — — — — — Enhanced equipment trust certificates (“EETC”) 22 — — 22 23 — — 23 Available-for-sale available-for-sale. Restricted cash Equity securities available-for-sale. Investments presented in the table above have the same fair value as their carrying value. The table below presents the carrying values and estimated fair values of financial instruments not presented in the tables above as of December 31 (in millions): Fair Value of Debt by Fair Value Hierarchy Level 2017 2016 Carrying Fair Value Carrying Fair Value Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Long-term debt $ 13,268 $ 13,787 $ — $ 10,115 $ 3,672 $ 10,767 $ 11,055 $ — $ 8,184 $ 2,871 Fair value of the financial instruments included in the tables above was determined as follows: Description Fair Value Methodology Cash and cash equivalents The carrying amounts approximate fair value because of the short-term maturity of these assets. Short-term investments, Equity securities, EETC and Restricted cash Fair value is based on (a) the trading prices of the investment or similar instruments, (b) an income approach, which uses valuation techniques to convert future amounts into a single present amount based on current market expectations about those future amounts when observable trading prices are not available, or (c) broker quotes obtained by third-party valuation services. Other investments measured at NAV In accordance with the relevant accounting standards, certain investments that are measured at fair value using the NAV per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in the table above are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statement of financial position. The investments measured using NAV are shares of mutual funds that invest in fixed-income instruments including bonds, debt securities, and other similar instruments issued by various U.S. and non-U.S. three-day Long-term debt Fair values were based on either market prices or the discounted amount of future cash flows using our current incremental rate of borrowing for similar liabilities.

Debt

Debt	12 Months Ended
	Dec. 31, 2017
Debt	NOTE 10 - DEBT (In millions) At December 31, 2017 2016 Secured Notes payable, fixed interest rates of 2.88% to 9.52% (weighted average rate of 4.39% as of December 31, 2017), payable through 2028 $ 8,661 $ 7,586 Notes payable, floating interest rates of the London interbank offered rate (“LIBOR”) plus 0.2% to 2.25%, payable through 2028 1,880 1,546 Term loan, LIBOR plus 2.00%, or alternative rate based on certain market rates plus 1.00%, due 2024 1,489 — Term loan, LIBOR subject to a 0.75% floor, plus 2.50%, or alternative rate based on certain market rates plus 1.50%, due 2019 — 866 Term loan, LIBOR subject to a 0.75% floor, plus 2.75%, or alternative rate based on certain market rates plus 1.75%, due 2021 — 192 Unsecured 6.375% Senior Notes due 2018 (a) 300 300 6% Senior Notes due 2020 (a) 300 300 4.25% Senior Notes due 2022 (a) 400 — 5% Senior Notes due 2024 (a) 300 — Other 101 101 13,431 10,891 Less: unamortized debt discount, premiums and debt issuance costs (163) (124) Less: current portion of long-term debt (1,565) (849) Long-term debt, net $ 11,703 $ 9,918 (a) UAL is the issuer of this debt. United is a guarantor. The table below presents the Company’s contractual principal payments (not including debt discount or debt issuance costs) at December 31, 2017 under then-outstanding long-term debt agreements in each of the next five calendar years (in millions): 2018 $ 1,565 2019 1,165 2020 1,170 2021 1,157 2022 1,492 After 2022 6,882 $ 13,431 Secured debt 2017 Credit and Guaranty Agreement. take-off Borrowings under the 2017 Credit Agreement bear interest at a variable rate equal to LIBOR plus a margin of 2.00% per annum, or another rate based on certain market interest rates, plus a margin of 1.00% per annum. The principal amount of the term loan must be repaid in consecutive quarterly installments of 0.25% of the original principal amount thereof, commencing on June 30, 2017, with any unpaid balance due on April 1, 2024. United may prepay all or a portion of the loan from time to time, at par plus accrued and unpaid interest. United pays a commitment fee equal to 0.75% per annum on the undrawn amount available under the revolving credit facility. As of December 31, 2017, United had its entire capacity of $2.0 billion available under the revolving credit facility of the Company’s 2017 Credit Agreement. As of December 31, 2017, United had cash collateralized $75 million of letters of credit. United also had $362 million of surety bonds securing various obligations at December 31, 2017. Most of the letters of credit have evergreen clauses and are expected to be renewed on an annual basis. The surety bonds have expiration dates through 2021. EETCs. In February 2018, November 2017, September 2016 and June 2016, United created separate EETC pass-through trusts, each of which issued pass-through certificates. The proceeds of the issuance of the pass-through certificates are used to purchase equipment notes issued by United and secured by its aircraft. The Company records the debt obligation upon issuance of the equipment notes rather than upon the initial issuance of the pass-through certificates. Certain details of the pass-through trusts with proceeds received from issuance of debt in 2017 are as follows (in millions, except stated interest rate): EETC Date Class Principal Final expected Stated Total debt recorded Proceeds Remaining February 2018 AA $ 677 March 2030 3.50% $ — $ — $ 677 February 2018 A 258 March 2030 3.70% — — 258 November 2017 B 258 January 2026 3.65% 258 258 — November 2017 B 236 October 2025 3.65% 236 236 — September 2016 AA 637 October 2028 2.875% 637 557 — September 2016 A 283 October 2028 3.10% 283 247 — June 2016 AA 729 July 2028 3.10% 729 319 — June 2016 A 324 July 2028 3.45% 324 142 — $ 3,402 $ 2,467 $ 1,759 $ 935 In 2017, United borrowed approximately $497 million aggregate principal amount from various financial institutions to finance the purchase of several aircraft delivered in 2017. The notes evidencing these borrowings, which are secured by the related aircraft, mature in 2027 and have interest rates comprised of the LIBOR plus a specified margin. Unsecured debt 4.25% Senior Notes due 2022. 5% Senior Notes due 2024. As of December 31, 2017, UAL and United were in compliance with their respective debt covenants. The collateral, covenants and cross default provisions of the Company’s principal debt instruments that contain such provisions are summarized in the table below: Debt Instrument Collateral, Covenants and Cross Default Provisions Various equipment notes and other notes payable Secured by certain aircraft. The indentures contain events of default that are customary for aircraft financing, including in certain cases cross default to other related aircraft. Credit Agreement Secured by certain of United’s international route authorities, specified take-off The 2017 Credit Agreement requires the Company to maintain at least $2.0 billion of unrestricted liquidity at all times, which includes unrestricted cash, short-term investments and any undrawn amounts under any revolving credit facility, and to maintain a minimum ratio of appraised value of collateral to the outstanding obligations under the 2017 Credit Agreement of 1.6 to 1.0 at all times. The 2017 Credit Agreement contains covenants that, among other things, restrict the ability of UAL and its restricted subsidiaries (as defined in the 2017 Credit Agreement) to incur additional indebtedness and to pay dividends on or repurchase stock, although the Company currently has ample ability under these restrictions to repurchase stock under the Company’s share repurchase program. The 2017 Credit Agreement contains events of default customary for this type of financing, including a cross default and cross acceleration provision to certain other material indebtedness of the Company. 6.375% Senior Notes due 2018 6% Senior Notes due 2020 4.25% Senior Notes due 2022 5% Senior Notes due 2024 The indentures for these notes contain covenants that, among other things, restrict the ability of the Company and its restricted subsidiaries (as defined in the indentures) to incur additional indebtedness and pay dividends on or repurchase stock, although the Company currently has ample ability under these restrictions to repurchase stock under the Company’s share repurchase program.

Leases and Capacity Purchase Ag

Leases and Capacity Purchase Agreements	12 Months Ended
	Dec. 31, 2017
Leases and Capacity Purchase Agreements	NOTE 11 - LEASES AND CAPACITY PURCHASE AGREEMENTS United leases aircraft, airport passenger terminal space, aircraft hangars and related maintenance facilities, cargo terminals, other airport facilities, other commercial real estate, office and computer equipment and vehicles. At December 31, 2017, United’s scheduled future minimum lease payments under operating leases having initial or remaining noncancelable lease terms of more than one year, aircraft leases, including aircraft rent under CPAs and capital leases (substantially all of which are for aircraft) were as follows (in millions): Capital Leases (a) Facility and Other Aircraft Operating 2018 $ 200 $ 1,234 $ 1,038 2019 133 1,075 855 2020 113 1,169 628 2021 110 935 510 2022 105 797 388 After 2022 1,156 6,109 1,513 Minimum lease payments $ 1,817 $ 11,319 $ 4,932 Imputed interest (693) Present value of minimum lease payments 1,124 Current portion (128) Long-term obligations under capital leases $ 996 (a) Includes airport construction projects managed by United in which United has construction risk, including project cost overruns. The Company recorded an asset for project costs and a related liability equal to project costs funded by parties other than United. As of December 31, 2017, United had an asset balance of $814 million recorded in operating property and equipment and $777 million recorded in current and long-term obligations under capital leases for these airport construction projects. As of December 31, 2017, United’s aircraft capital lease minimum payments relate to leases of 31 mainline and 43 regional aircraft as well as to leases of nonaircraft assets. Imputed interest rate ranges are 3.5% to 20.8%. Aircraft operating leases have initial terms of five to 26 years, with expiration dates ranging from 2018 through 2029. Under the terms of most leases, United has the right to purchase the aircraft at the end of the lease term, in some cases, at fair market value, and in others, at fair market value or a percentage of cost. During 2015, the Company reached an agreement with AerCap Holdings N.V., a major aircraft leasing company, to lease used Airbus S.A.S (“Airbus”) A319s. Eleven aircraft have been delivered since the inception of this agreement, and seven more aircraft are expected to be delivered between 2019 and 2020. In addition, United has options for seven more A319 aircraft, subject to certain conditions. United is the lessee of real property under long-term operating leases at a number of airports where we are also the guarantor of approximately $1.4 billion of underlying debt and interest thereon as of December 31, 2017. These leases are typically with municipalities or other governmental entities, which are excluded from the consolidation requirements concerning a variable interest entity (“VIE”). To the extent United’s leases and related guarantees are with a separate legal entity other than a governmental entity, United is not the primary beneficiary because the lease terms are consistent with market terms at the inception of the lease and the lease does not include a residual value guarantee, fixed-price purchase option, or similar feature. United has facility operating leases that extend to 2054. United’s nonaircraft rent expense was approximately $1.3 billion, $1.2 billion and $1.3 billion for the years ended December 31, 2017, 2016 and 2015, respectively. In addition to nonaircraft rent and aircraft rent, which is separately presented in the consolidated statements of operations, United had aircraft rent related to regional aircraft operating leases, which is included as part of Regional capacity purchase expense in United’s consolidated statement of operations, of $458 million, $439 million and $461 million for the years ended December 31, 2017, 2016 and 2015, respectively. In connection with UAL Corporation’s and United Air Lines, Inc.’s (predecessors to UAL and United) fresh-start reporting requirements upon their exit from Chapter 11 bankruptcy protection in 2006 and the Company’s acquisition accounting adjustments related to the Company’s merger transaction in 2010, lease valuation adjustments for operating leases were initially recorded in the consolidated balance sheet, representing the net present value of the differences between contractual lease rates and the fair market lease rates for similar leased assets at the time. An asset (liability) results when the contractual lease rates are more (less) favorable than market lease terms at the valuation date. The lease valuation adjustment is amortized on a straight-line basis as an increase (decrease) to rent expense over the individual applicable remaining lease terms, resulting in recognition of rent expense as if United had entered into the leases at market rates. The related remaining lease terms, primarily related to aircraft which make up the majority of the fair value lease adjustment balance, are one to seven years for United. The lease valuation adjustments are classified within other noncurrent liabilities and the net accretion amounts are $79 million, $82 million and $107 million for the years ended December 31, 2017, 2016 and 2015, respectively. Regional CPAs United has contractual relationships with various regional carriers to provide regional aircraft service branded as United Express. Under these CPAs, the Company pays the regional carriers contractually agreed fees (carrier costs) for operating these flights plus a variable reimbursement (incentive payment for operational performance) based on agreed performance metrics, subject to annual inflation adjustments. The fees for carrier costs are based on specific rates for various operating expenses of the regional carriers, such as crew expenses, maintenance and aircraft ownership, some of which are multiplied by specific operating statistics (e.g., block hours, departures), while others are fixed monthly amounts. Under these CPAs, the Company is responsible for all fuel costs incurred, as well as landing fees and other costs, which are either passed through by the regional carrier to the Company without any markup or directly incurred by the Company. United’s CPAs are for 518 regional aircraft as of December 31, 2017, and the CPAs have terms expiring through 2029. Aircraft operated under CPAs include aircraft leased directly from the regional carriers and those owned by United or leased from third-party lessors and operated by the regional carriers. See Part I, Item 2, Properties, of this report for additional information. In 2017, United entered into a five-year CPA with Air Wisconsin Airlines for regional service under the United Express brand to operate up to 65 CRJ200 aircraft. In addition, United extended the term of its existing CPA with ExpressJet Airlines to operate up to approximately 125 aircraft through December 31, 2022. In January 2018, United removed all Bombardier Q200 turboprop aircraft and Embraer ERJ 135 aircraft from service. United holds a minority equity interest in two of its regional carriers, Champlain Enterprises, Inc. and Republic Airways Holdings, Inc. The contracts with these related parties are executed in the ordinary course of business. United recorded approximately $538 million, $486 million and $366 million in expenses related to its capacity purchase agreements with these regional carriers for the years ended December 31, 2017, 2016 and 2015, respectively. There were approximately $24 million and $32 million in accounts payable due to these companies as of December 31, 2017 and December 31, 2016, respectively. There were no material accounts receivable due from these companies as of December 31, 2017 and December 31, 2016. Our future commitments under our CPAs are dependent on numerous variables, and are, therefore, difficult to predict. The most important of these variables is the number of scheduled block hours. Although we are not required to purchase a minimum number of block hours under certain of our CPAs, we have set forth below estimates of our future payments under the CPAs based on our assumptions. United’s estimates of its future payments under all of the CPAs do not include the portion of the underlying obligation for any aircraft leased to a regional carrier or deemed to be leased from other regional carriers and facility rent that are disclosed as part of aircraft and nonaircraft operating leases. For purposes of calculating these estimates, we have assumed (1) the number of block hours flown is based on our anticipated level of flight activity or at any contractual minimum utilization levels if applicable, whichever is higher, (2) that we will reduce the fleet as rapidly as contractually allowed under each CPA, (3) that aircraft utilization, stage length and load factors will remain constant, (4) that each carrier’s operational performance will remain at historic levels and (5) an annual projected inflation rate. These amounts exclude variable pass-through costs such as fuel and landing fees, among others. Based on these assumptions as of December 31, 2017, our future payments through the end of the terms of our CPAs are presented in the table below (in billions): 2018 $ 2.0 2019 1.8 2020 1.6 2021 1.5 2022 1.4 After 2022 3.2 $ 11.5 The actual amounts we pay to our regional operators under CPAs could differ materially from these estimates. For example, a 10% increase or decrease in scheduled block hours for all of United’s regional operators (whether as a result of changes in average daily utilization or otherwise) in 2018 would result in a corresponding change in annual cash obligations under the CPAs of approximately $147 million.

Variable Interest Entities

Variable Interest Entities	12 Months Ended
	Dec. 31, 2017
Variable Interest Entities	NOTE 12 - VARIABLE INTEREST ENTITIES Variable interests are contractual, ownership or other monetary interests in an entity that change with fluctuations in the fair value of the entity’s net assets exclusive of variable interests. A VIE can arise from items such as lease agreements, loan arrangements, guarantees or service contracts. An entity is a VIE if (a) the entity lacks sufficient equity or (b) the entity’s equity holders lack power or the obligation and right as equity holders to absorb the entity’s expected losses or to receive its expected residual returns. Therefore, if the equity owners as a group do not have the power to direct the entity’s activities that most significantly impact its economic performance, the entity is a VIE. If an entity is determined to be a VIE, the entity must be consolidated by the primary beneficiary. The primary beneficiary is the holder of the variable interests that has the power to direct the activities of a VIE that (i) most significantly impact the VIE’s economic performance and (ii) has the obligation to absorb losses of or the right to receive benefits from the VIE that could potentially be significant to the VIE. Therefore, the Company must identify which activities most significantly impact the VIE’s economic performance and determine whether it, or another party, has the power to direct those activities. The Company’s evaluation of its association with VIEs is described below: Aircraft Leases EETCs. The primary risk of the pass-through trusts is credit risk (i.e. the risk that United, the issuer of the equipment notes, may be unable to make its principal and interest payments). The primary purpose of the pass-through trust structure is to enhance the credit worthiness of United’s debt obligation through certain bankruptcy protection provisions, a liquidity facility (in certain of the EETC structures) and improved loan-to-value United does not invest in or obtain a financial interest in the pass-through trusts. Rather, United has an obligation to make interest and principal payments on its equipment notes held by the pass-through trusts. United did not intend to have any voting or non-voting

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2017
COMMITMENTS AND CONTINGENCIES	NOTE 13 - COMMITMENTS AND CONTINGENCIES Commitments. Aircraft Type Number of Firm Airbus A350 45 Boeing 737 MAX 161 Boeing 777-300ER 4 Boeing 787 18 (a) United also has options and purchase rights for additional aircraft. The aircraft listed in the table above are scheduled for delivery from 2018 through 2027. In 2018, United expects to take delivery of 10 Boeing 737 MAX aircraft, seven Boeing 787 aircraft and four Boeing 777-300ER 767-300ER The table below summarizes United’s commitments as of December 31, 2017, which primarily relate to the acquisition of aircraft and related spare engines, aircraft improvements and include other capital purchase commitments for the years ended December 31 (in billions). Any new firm aircraft orders, including through the exercise of purchase options and purchase rights, will increase the total future capital commitments of the Company. 2018 $ 3.2 2019 2.9 2020 2.1 2021 2.4 2022 1.8 After 2022 9.8 $ 22.2 In February 2018, the Company secured $935 million of EETC financing to finance certain aircraft deliveries in 2017 and the first half of 2018. The Company has also secured backstop financing commitments from certain of its aircraft manufacturers for a limited number of its future aircraft deliveries, subject to certain customary conditions. Financing may be necessary to satisfy the Company’s capital commitments for its firm order aircraft and other related capital expenditures. Legal and Environmental. Guarantees and Indemnifications. As of December 31, 2017, United is the guarantor of approximately $1.8 billion in aggregate principal amount of tax-exempt tax-exempt Increased Cost Provisions. non-U.S. non-U.S. As of December 31, 2017, United is the guarantor of $157 million of aircraft mortgage debt issued by one of United’s regional carriers. The aircraft mortgage debt is subject to similar increased cost provisions as described above for the Company’s debt, and the Company would potentially be responsible for those costs under the guarantees. Fuel Consortia. tax-exempt tax-exempt Regional Capacity Purchase. Credit Card Processing Agreements. Labor Negotiations. UNITE HERE is attempting to organize United’s Catering Operations employees, who are currently unrepresented, and filed an application to do so with the National Mediation Board on January 24, 2018.

SPECIAL CHARGES

SPECIAL CHARGES	12 Months Ended
	Dec. 31, 2017
SPECIAL CHARGES	NOTE 14 - SPECIAL CHARGES Special charges in the statements of consolidated operations consisted of the following for the years ended December 31 (in millions): Operating: 2017 2016 2015 Severance and benefit costs $ 116 $ 37 $ 107 Impairment of assets 25 412 79 Cleveland airport lease restructuring — 74 — Labor agreement costs — 64 18 (Gains) losses on sale of assets and other special charges 35 51 122 Total operating special charges 176 638 326 Nonoperating: (Gains) losses on extinguishment of debt and other — (1) 202 Total operating and nonoperating special charges before income taxes 176 637 528 Income tax benefit related to special charges (63) (229) (11) Income tax adjustments (Notes 6 and 7) (192) 180 (3,130) Total operating and nonoperating special charges, net of income taxes and income tax adjustments $ (79) $ 588 $ (2,613) 2017 During 2017, the Company recorded $83 million ($53 million net of taxes) of severance and benefit costs related to a voluntary early-out During 2017 the Company recorded a $10 million ($6 million net of taxes) impairment charge related to obsolete spare parts inventory and a $15 million ($10 million net of taxes) intangible asset impairment charge related to a maintenance service agreement. 2016 In April 2016, the Federal Aviation Administration (“FAA”) announced that it will designate Newark Liberty International Airport (“Newark”) as a Level 2 schedule-facilitated airport under the International Air Transport Association Worldwide Slot Guidelines. The designation was associated with an updated demand and capacity analysis of Newark by the FAA. In 2016, the Company determined that the FAA’s action impaired the entire value of its Newark slots because the slots are no longer the mechanism that governs take-off In 2016, the City of Cleveland agreed to amend the Company’s lease, which runs through 2029, associated with certain excess airport terminal space (principally Terminal D) and related facilities at Hopkins International Airport (“Cleveland”). The Company recorded an accrual for remaining payments under the lease for facilities that the Company no longer uses and will continue to incur costs under the lease without economic benefit to the Company. This liability was measured and recorded at its fair value when the Company ceased its right to use such facilities leased to it pursuant to the lease. The Company recorded a net charge of $74 million ($47 million net of taxes) related to the amended lease. The fleet service, passenger service, storekeeper and other employees represented by the International Association of Machinists and Aerospace Workers (the “IAM”) ratified seven new contracts with the Company which extended the contracts through 2021. The technicians and related employees represented by the IBT ratified a six-year one-time one-time During 2016, the Company recorded $37 million ($24 million net of taxes) of severance and benefit costs related to a voluntary early-out 2015 During its annual assessment in the fourth quarter, the Company recorded $33 million ($22 million net of related income tax benefit) related to the impairment of its indefinite-lived intangible assets (certain domestic slots and international Pacific routes), $8 million for the write-off The Company recorded $107 million of severance and benefit costs primarily related to a voluntary early-out During 2015, the Company also recorded $18 million related to collective bargaining agreements, $60 million of integration-related costs primarily related to systems integration and training for employees, $32 million related to charges for settlements in connection with legal matters, $16 million for the cease use of an aircraft under lease and $14 million for losses on the sale of aircraft and other miscellaneous gains and losses. The Company recorded $202 million of losses as part of Nonoperating income (expense): Miscellaneous, net due primarily to the write-off non-cash mid-2014. As Accrual Activity Activity related to the accruals for severance and medical costs and future lease payments on permanently grounded aircraft is as follows (in millions): Severance/ Permanently Balance at December 31, 2014 $ 109 $ 102 Accrual 107 30 Payments (189) (54) Balance at December 31, 2015 27 78 Accrual and related adjustments 37 (17) Payments (50) (20) Balance at December 31, 2016 14 41 Accrual 116 (4) Payments (93) (15) Balance at December 31, 2017 $ 37 $ 22 The Company’s accrual and payment activity is primarily related to severance and other compensation expense associated with voluntary employee early retirement programs.

SEGMENT INFORMATION

SEGMENT INFORMATION	12 Months Ended
	Dec. 31, 2017
SEGMENT INFORMATION	NOTE 15 - SEGMENT INFORMATION Operating segments are defined as components of an enterprise with separate financial information, which are evaluated regularly by the chief operating decision maker and are used in resource allocation and performance assessments. The Company deploys its aircraft across its route network through a single route scheduling system to maximize its value. When making resource allocation decisions, the Company’s chief operating decision maker evaluates flight profitability data, which considers aircraft type and route economics. The Company’s chief operating decision maker makes resource allocation decisions to maximize the Company’s consolidated financial results. Managing the Company as one segment allows management the opportunity to maximize the value of its route network. The Company’s operating revenue by principal geographic region (as defined by the U.S. Department of Transportation) for the years ended December 31 is presented in the table below (in millions): 2017 2016 2015 Domestic (U.S. and Canada) $ 23,131 $ 22,202 $ 21,931 Pacific 4,898 4,959 5,498 Atlantic 6,285 6,157 7,068 Latin America 3,422 3,238 3,367 Total $ 37,736 $ 36,556 $ 37,864 The Company attributes revenue among the geographic areas based upon the origin and destination of each flight segment. The Company’s operations involve an insignificant level of dedicated revenue-producing assets in geographic regions as the overwhelming majority of the Company’s revenue producing assets (primarily U.S. registered aircraft) can be deployed in any of its geographic regions.

SELECTED QUARTERLY FINANCIAL DA

SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED)	12 Months Ended
	Dec. 31, 2017
SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED)	NOTE 16 - SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) UAL Quarter Ended (In millions, except per share amounts) March 31 June 30 September 30 December 31 2017 Operating revenue $ 8,420 $ 10,000 $ 9,878 $ 9,438 Income from operations 278 1,399 1,092 729 Net income 96 818 637 580 Basic earnings per share 0.31 2.67 2.12 1.99 Diluted earnings per share 0.31 2.66 2.12 1.99 2016 Operating revenue $ 8,195 $ 9,396 $ 9,913 $ 9,052 Income from operations 649 1,060 1,624 1,005 Net income 313 588 965 397 Basic earnings per share 0.88 1.78 3.02 1.26 Diluted earnings per share 0.88 1.78 3.01 1.26 UAL’s quarterly financial data is subject to seasonal fluctuations and historically its second and third quarter financial results, which reflect higher travel demand, are better than its first and fourth quarter financial results. UAL’s quarterly results were impacted by the following significant items (in millions): Quarter Ended March 31 June 30 September 30 December 31 2017 Operating: Severance and benefit costs $ 37 $ 41 $ 23 $ 15 Impairment of assets — — 15 10 (Gains) losses on sale of assets and other special charges 14 3 12 6 Total operating special charges 51 44 50 31 Income taxes: Income tax benefit related to special charges (18) (16) (18) (11) Income tax adjustments (Note 7) — — — (192) Total operating special charges, net of income taxes and income tax adjustments $ 33 $ 28 $ 32 $ (172) 2016 Operating: Labor agreement costs and related items $ 100 $ 10 $ 14 $ (60) Cleveland airport lease restructuring 74 — — — Severance and benefit costs 8 6 13 10 Impairment of assets — 412 — — (Gains) losses on sale of assets and other special charges 8 6 18 19 Total operating special charges 190 434 45 (31) Nonoperating and income taxes: Losses (gain) on extinguishment of debt and other 8 (9) — — Income tax expense (benefit) related to special charges (72) (153) (16) 12 Income tax adjustments (Note 6) — — — 180 Total operating and nonoperating special charges, net of income taxes and income tax adjustments $ 126 $ 272 $ 29 $ 161

Schedule II Valuation and Quali

Schedule II Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2017
Schedule II Valuation and Qualifying Accounts	Schedule II Valuation and Qualifying Accounts For the Years Ended December 31, 2017, 2016 and 2015 (In millions) Description Balance at Beginning of Period Additions Charged to Costs and Expenses Deductions (a) Other Balance at End of Period Allowance for doubtful accounts—UAL and United: 2017 $ 10 $ 20 $ 23 $ — $ 7 2016 18 18 26 — 10 2015 22 25 29 — 18 Obsolescence allowance—spare parts—UAL and United: 2017 $ 295 $ 75 $ 17 $ 1 $ 354 2016 235 61 16 15 295 2015 169 38 — 28 235 Valuation allowance for deferred tax assets—UAL: 2017 $ 68 $ 11 $ 27 $ 11 $ 63 2016 48 47 27 — 68 2015 4,751 — 4,703 — 48 Valuation allowance for deferred tax assets—United: 2017 $ 68 $ 11 $ 27 $ 11 $ 63 2016 48 47 27 — 68 2015 4,721 — 4,673 — 48 (a) Deduction from reserve for purpose for which reserve was created.

Significant Accounting Polici25

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Use of Estimates	(a) Use of Estimates—
Revenue Recognition	(b) Revenue Recognition— Non-refundable Fees charged in association with changes or extensions to non-refundable non-refundable The Company records an estimate of breakage revenue on the flight date for tickets that will expire unused. These estimates are based on the evaluation of actual historical results and forecasted trends. Refundable tickets expire after one year from the date of issuance. The Company recognizes cargo and other revenue as service is provided. Under our capacity purchase agreements (“CPAs”) with regional carriers, we purchase all of the capacity related to aircraft covered by the contracts and are responsible for selling all of the related seat inventory. We record the passenger revenue and related expenses as separate operating revenue and expense in the consolidated statement of operations. Accounts receivable primarily consist of amounts due from credit card companies and customers of our aircraft maintenance and cargo transportation services. We provide an allowance for uncollectible accounts equal to the estimated losses expected to be incurred based on historical write-offs and other specific analyses. Bad debt expense and write-offs were not material for the years ended December 31, 2017, 2016 and 2015.
Frequent Flyer Accounting	(c) Frequent Flyer Accounting— non-airline non-travel Miles Earned in Conjunction with Flights When frequent flyers earn miles for flights, the Company recognizes a portion of the ticket sales as revenue when the air transportation occurs and defers a portion of the ticket sale representing the value of the related miles as a multiple-deliverable revenue arrangement. The Company determines the estimated selling price of air transportation and miles as if each element is sold on a separate basis. The total consideration from each ticket sale is then allocated to each of these elements, individually, on a pro rata basis. The miles are recorded in Frequent flyer deferred revenue on the Company’s consolidated balance sheet and recognized into revenue when the transportation is provided. The Company’s estimated selling price of miles is based on an equivalent ticket value less fulfillment discount, which incorporates the expected redemption of miles, as the best estimate of selling price for these miles. The equivalent ticket value is based on the prior 12 months’ weighted average equivalent ticket value of similar fares as those used to settle award redemptions while taking into consideration such factors as redemption pattern, cabin class, loyalty status and geographic region. The estimated selling price of miles is adjusted by a fulfillment discount that considers a number of factors, including redemption patterns of various customer groups. Co-branded United has a significant contract, the Second Amended and Restated Co-Branded “Co-Brand co-branded Co-Brand The fair value of the elements is determined using management’s estimated selling price of each element. The objective of using the estimated selling price based methodology is to determine the price at which we would transact a sale if the product or service were sold on a stand-alone basis. Accordingly, we determine our best estimate of selling price by considering multiple inputs and methods including, but not limited to, discounted cash flows, brand value, volume discounts, published selling prices, number of miles awarded and number of miles redeemed. The Company estimated the selling prices and volumes over the term of the Co-Brand The Company records passenger revenue related to the air transportation element when the transportation is delivered. The other elements are generally recognized as Other operating revenue when earned. Expiration of Miles The Company accounts for miles sold and awarded that will never be redeemed by program members, which we refer to as breakage. The Company reviews its breakage estimates annually based upon the latest available information regarding redemption and expiration patterns. Miles expire after 18 months of member account inactivity. The Company’s estimate of the expected expiration of miles requires significant management judgment. Current and future changes to expiration assumptions or to the expiration policy, or to program rules and program redemption opportunities, may result in material changes to the deferred revenue balance as well as recognized revenues from the programs. Other Information The following table provides additional information related to the frequent flyer program (in millions): Year Ended December 31, Cash Proceeds Other Revenue Recognized Upon Award of Miles Increase in Frequent Flyer Deferred Decrease in of Miles (c) 2017 $ 2,343 $ 1,183 $ 2,025 $ (865) 2016 3,022 1,221 2,050 (249) 2015 2,999 1,050 2,173 (224) (a) This amount represents other revenue recognized during the period from the sale of miles to third parties, representing the marketing-related deliverable services component of the sale. (b) This amount represents the increase to Frequent flyer deferred revenue during the period. (c) This amount represents the net decrease in the advance purchase of miles obligation due to cash payments for the sale of miles less than miles awarded to customers.
Cash and Cash Equivalents and Restricted Cash	(d) Cash and Cash Equivalents and Restricted Cash— Restricted cash primarily includes cash collateral for letters of credit and collateral associated with obligations for facility leases and workers’ compensation. Restricted cash is classified as short-term or long-term in the consolidated balance sheets based on the expected timing of return of the assets to the Company. The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the consolidated balance sheets that sum to the total of the same such amounts shown in the statements of consolidated cash flows: UAL United At December 31, At December 31, 2017 2016 2015 2017 2016 2015 Current assets: Cash and cash equivalents $ 1,482 $ 2,179 $ 3,006 $ 1,476 $ 2,173 $ 3,000 Restricted cash included in Prepaid expenses and other 18 — 2 18 — 2 Other assets: Restricted cash 91 124 204 91 124 204 Total cash, cash equivalents and restricted cash shown in the statement of consolidated cash flows $ 1,591 $ 2,303 $ 3,212 $ 1,585 $ 2,297 $ 3,206
Short-term Investments	(e) Short-term Investments— available-for-sale available-for-sale
Aircraft Fuel, Spare Parts and Supplies	(f) Aircraft Fuel, Spare Parts and Supplies—
Property and Equipment	(g) Property and Equipment— Depreciation and amortization of owned depreciable assets is based on the straight-line method over the assets’ estimated useful lives. Leasehold improvements are amortized over the remaining term of the lease, including estimated facility renewal options when renewal is reasonably assured at key airports, or the estimated useful life of the related asset, whichever is less. Properties under capital leases are amortized on the straight-line method over the life of the lease or, in the case of certain aircraft, over their estimated useful lives, whichever is shorter. Amortization of capital lease assets is included in depreciation and amortization expense. The estimated useful lives of property and equipment are as follows: Estimated Useful Life (in years) Aircraft and related rotable parts 25 to 30 Buildings 25 to 45 Other property and equipment 3 to 15 Computer software 5 to 15 Building improvements 1 to 40 As of December 31, 2017 and 2016, the Company had a carrying value of computer software of $345 million and $356 million, respectively. For the years ended December 31, 2017, 2016 and 2015, the Company’s depreciation expense related to computer software was $117 million, $108 million and $93 million, respectively. Aircraft and aircraft spare parts were assumed to have residual values of approximately 10% of original cost, and other categories of property and equipment were assumed to have no residual value.
Maintenance and Repairs	(h) Maintenance and Repairs— power-by-the-hour
Lease Fair Value Adjustments	(i) Lease Fair Value Adjustments—
Regional Capacity Purchase	(j) Regional Capacity Purchase—
Advertising	(k) Advertising—
Intangibles	(l) Intangibles—
Long-Lived Asset Impairments	(m) Long-Lived Asset Impairments—
Share-Based Compensation	(n) Share-Based Compensation—
Ticket Taxes	(o) Ticket Taxes—
Retirement of Leased Aircraft	(p) Retirement of Leased Aircraft—
Uncertain Income Tax Positions	(q) Uncertain Income Tax Positions—
Labor Costs	(r) Labor Costs—
Third-Party Business	(s) Third-Party Business— non-air non-air
Recently Issued Accounting Standards	(t) Recently Issued Accounting Standards— Revenue from Contracts with Customers . Revenue Recognition Statements of Consolidated Operations for the Years Ended December 31, As Reported Adjustment As Adjusted for Adoption of 2017 2016 2017 2016 2017 2016 Operating revenue: Passenger—Mainline $ 26,552 $ 25,414 $ 1,707 $ 1,615 $ 28,259 $ 27,029 Passenger—Regional 5,852 6,043 349 357 6,201 6,400 Total passenger revenue 32,404 31,457 2,056 1,972 34,460 33,429 Cargo 1,035 876 79 58 1,114 934 Other operating revenue 4,297 4,223 (2,087) (2,028) 2,210 2,195 Total operating revenue 37,736 36,556 48 2 37,784 36,558 Operating expenses 34,238 32,218 (21) (12) 34,217 32,206 Operating income 3,498 4,338 69 14 3,567 4,352 Nonoperating expense, net (499) (519) (28) (60) (527) (579) Income before income taxes 2,999 3,819 41 (46) 3,040 3,773 Income tax expense (benefit) 868 1,556 28 (17) 896 1,539 Net income $ 2,131 $ 2,263 $ 13 $ (29) $ 2,144 $ 2,234 Earnings per share, basic $ 7.04 $ 6.86 $ 0.04 $ (0.09) $ 7.08 $ 6.77 Earnings per share, diluted $ 7.02 $ 6.85 $ 0.04 $ (0.09) $ 7.06 $ 6.76 Consolidated Balance Sheets as of December 31, As Reported Adjustment As Adjusted for Adoption of 2017 2016 2017 2016 2017 2016 Current assets: Prepaid expenses and other $ 1,051 $ 832 $ 20 $ 20 $ 1,071 $ 852 Other assets: Deferred income taxes — 655 — 48 — 703 Current liabilities: Advance ticket sales 3,876 3,730 64 65 3,940 3,795 Frequent flyer deferred revenue 2,176 2,135 16 14 2,192 2,149 Other 569 1,010 7 79 576 1,089 Other liabilities and deferred credits: Frequent flyer deferred revenue 2,565 2,748 26 (8 ) 2,591 2,740 Advanced purchase of miles — 430 — 3 — 433 Deferred income taxes 225 — (21) — 204 — Stockholders’ equity: Retained earnings 4,621 3,427 (72) (85 ) 4,549 3,342 In 2016, the FASB amended the FASB Accounting Standards Codification and created a new Topic 842, Leases right-of-use Leases In 2016, the FASB issued Accounting Standards Update No. 2016-01, Financial Instruments—Overall 825-10) 2016-01”). available-for-sale 2016-01 In 2017, the FASB issued Accounting Standards Update No. 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost 2017-07”). . 2017-07 2017-07 2017-07 Statements of Consolidated Operations for the Years Ended December 31, As Reported Adjustment As Adjusted for Adoption of ASU 2017-07 2017 2016 2017 2016 2017 2016 Operating expense: Salaries and related costs $ 11,045 $ 10,275 $ (104) $ (99 ) $ 10,941 $ 10,176 Special charges 176 638 — 107 176 745 Nonoperating income (expense): Miscellaneous, net 3 (19) (104) 8 (101) (11) In February 2018, the FASB issued Accounting Standards Update No. 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income 2018-02”). 2018-02

Significant Accounting Polici26

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Schedule of Information Related to Amounts Recorded Related to Frequent Flyer Programs	The following table provides additional information related to the frequent flyer program (in millions): Year Ended December 31, Cash Proceeds Other Revenue Recognized Upon Award of Miles Increase in Frequent Flyer Deferred Decrease in of Miles (c) 2017 $ 2,343 $ 1,183 $ 2,025 $ (865) 2016 3,022 1,221 2,050 (249) 2015 2,999 1,050 2,173 (224) (a) This amount represents other revenue recognized during the period from the sale of miles to third parties, representing the marketing-related deliverable services component of the sale. (b) This amount represents the increase to Frequent flyer deferred revenue during the period. (c) This amount represents the net decrease in the advance purchase of miles obligation due to cash payments for the sale of miles less than miles awarded to customers.
Schedule of Cash and Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the consolidated balance sheets that sum to the total of the same such amounts shown in the statements of consolidated cash flows: UAL United At December 31, At December 31, 2017 2016 2015 2017 2016 2015 Current assets: Cash and cash equivalents $ 1,482 $ 2,179 $ 3,006 $ 1,476 $ 2,173 $ 3,000 Restricted cash included in Prepaid expenses and other 18 — 2 18 — 2 Other assets: Restricted cash 91 124 204 91 124 204 Total cash, cash equivalents and restricted cash shown in the statement of consolidated cash flows $ 1,591 $ 2,303 $ 3,212 $ 1,585 $ 2,297 $ 3,206
Schedule of Cash and Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the consolidated balance sheets that sum to the total of the same such amounts shown in the statements of consolidated cash flows: UAL United At December 31, At December 31, 2017 2016 2015 2017 2016 2015 Current assets: Cash and cash equivalents $ 1,482 $ 2,179 $ 3,006 $ 1,476 $ 2,173 $ 3,000 Restricted cash included in Prepaid expenses and other 18 — 2 18 — 2 Other assets: Restricted cash 91 124 204 91 124 204 Total cash, cash equivalents and restricted cash shown in the statement of consolidated cash flows $ 1,591 $ 2,303 $ 3,212 $ 1,585 $ 2,297 $ 3,206
Estimated Useful Lives of Property and Equipment	The estimated useful lives of property and equipment are as follows: Estimated Useful Life (in years) Aircraft and related rotable parts 25 to 30 Buildings 25 to 45 Other property and equipment 3 to 15 Computer software 5 to 15 Building improvements 1 to 40
ASC 606
Schedule of Adoption of Accounting Standards and Expected Impact on Financial Statements	Statements of Consolidated Operations for the Years Ended December 31, As Reported Adjustment As Adjusted for Adoption of 2017 2016 2017 2016 2017 2016 Operating revenue: Passenger—Mainline $ 26,552 $ 25,414 $ 1,707 $ 1,615 $ 28,259 $ 27,029 Passenger—Regional 5,852 6,043 349 357 6,201 6,400 Total passenger revenue 32,404 31,457 2,056 1,972 34,460 33,429 Cargo 1,035 876 79 58 1,114 934 Other operating revenue 4,297 4,223 (2,087) (2,028) 2,210 2,195 Total operating revenue 37,736 36,556 48 2 37,784 36,558 Operating expenses 34,238 32,218 (21) (12) 34,217 32,206 Operating income 3,498 4,338 69 14 3,567 4,352 Nonoperating expense, net (499) (519) (28) (60) (527) (579) Income before income taxes 2,999 3,819 41 (46) 3,040 3,773 Income tax expense (benefit) 868 1,556 28 (17) 896 1,539 Net income $ 2,131 $ 2,263 $ 13 $ (29) $ 2,144 $ 2,234 Earnings per share, basic $ 7.04 $ 6.86 $ 0.04 $ (0.09) $ 7.08 $ 6.77 Earnings per share, diluted $ 7.02 $ 6.85 $ 0.04 $ (0.09) $ 7.06 $ 6.76 Consolidated Balance Sheets as of December 31, As Reported Adjustment As Adjusted for Adoption of 2017 2016 2017 2016 2017 2016 Current assets: Prepaid expenses and other $ 1,051 $ 832 $ 20 $ 20 $ 1,071 $ 852 Other assets: Deferred income taxes — 655 — 48 — 703 Current liabilities: Advance ticket sales 3,876 3,730 64 65 3,940 3,795 Frequent flyer deferred revenue 2,176 2,135 16 14 2,192 2,149 Other 569 1,010 7 79 576 1,089 Other liabilities and deferred credits: Frequent flyer deferred revenue 2,565 2,748 26 (8 ) 2,591 2,740 Advanced purchase of miles — 430 — 3 — 433 Deferred income taxes 225 — (21) — 204 — Stockholders’ equity: Retained earnings 4,621 3,427 (72) (85 ) 4,549 3,342
ASU 2017-07
Schedule of Adoption of Accounting Standards and Expected Impact on Financial Statements	Statements of Consolidated Operations for the Years Ended December 31, As Reported Adjustment As Adjusted for Adoption of ASU 2017-07 2017 2016 2017 2016 2017 2016 Operating expense: Salaries and related costs $ 11,045 $ 10,275 $ (104) $ (99 ) $ 10,941 $ 10,176 Special charges 176 638 — 107 176 745 Nonoperating income (expense): Miscellaneous, net 3 (19) (104) 8 (101) (11)

Goodwill and Other Intangible27

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Other Intangible Assets	The following table presents information about the Company’s goodwill and other intangible assets at December 31 (in millions): 2017 2016 Item Asset life (a) Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Goodwill $ 4,523 $ 4,523 Finite-lived intangible assets Frequent flyer database (b) 22 $ 1,177 $ 832 $ 1,177 $ 771 Hubs 20 145 89 145 82 Contracts 13 121 103 135 95 Patents and tradenames 3 108 108 108 108 Airport slots and gates 8 97 97 97 97 Other 25 109 84 109 81 Total $ 1,757 $ 1,313 $ 1,771 $ 1,234 Indefinite-lived intangible assets Route authorities $ 1,562 $ 1,562 Airport slots and gates 536 536 Tradenames and logos 593 593 Alliances 404 404 Total $ 3,095 $ 3,095 (a) Weighted average life expressed in years. (b) The frequent flyer database is amortized based on an accelerated amortization schedule to reflect utilization of the assets. Estimated cash flows correlating to the expected attrition rate of customers in the frequent flyer database is considered in the determination of the amortization schedules.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Computation of Earnings Per Share	The computations of UAL’s basic and diluted earnings per share are set forth below for the years ended December 31 (in millions, except per share amounts): 2017 2016 2015 Earnings available to common stockholders $ 2,131 $ 2,263 $ 7,340 Basic weighted-average shares outstanding 302.7 329.9 376.1 Effect of convertible notes — — 0.3 Effect of employee stock awards 0.9 0.4 0.5 Diluted weighted-average shares outstanding 303.6 330.3 376.9 Earnings per share, basic $ 7.04 $ 6.86 $ 19.52 Earnings per share, diluted $ 7.02 $ 6.85 $ 19.47

Share-Based Compensation Plans

Share-Based Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Schedule of Share-Based Compensation Plan Cost	The following table provides information related to UAL’s share-based compensation plan cost for the years ended December 31 (in millions): 2017 2016 2015 Compensation cost: RSUs $ 63 $ 58 $ 52 Restricted stock 8 11 6 Stock options 2 1 — Total $ 73 $ 70 $ 58
Schedule of Unearned Compensation and Weighted Average Remaining Period for Outstanding Share-Based Awards	The table below summarizes UAL’s unearned compensation and weighted-average remaining period to recognize costs for all outstanding share-based awards that are probable of being achieved as of December 31, 2017 (in millions, except as noted): Unearned Weighted- Average Remaining (in years) RSUs $ 46 1.9 Stock options 4 3.9 Restricted stock 3 1.2 Total $ 53
Schedule of Restricted Stock Unit and Restricted Stock Activity	The table below summarizes UAL’s RSUs and restricted stock activity for the years ended December 31 (shares in millions): RSUs Restricted Stock Weighted- Outstanding at December 31, 2014 3.8 0.7 $ 32.55 Granted 1.0 0.2 66.53 Vested (1.6) (0.4) 31.14 Forfeited (0.6) (0.2) 46.23 Outstanding at December 31, 2015 2.6 0.3 48.68 Granted 1.9 0.4 50.63 Vested (1.4) (0.1) 41.47 Forfeited (0.2) (0.1) 53.42 Outstanding at December 31, 2016 2.9 0.5 52.00 Granted 1.6 — — Vested (1.0) (0.2) 51.60 Forfeited (0.3) — 51.88 Outstanding at December 31, 2017 3.2 0.3 52.30

Accumulated Other Comprehensi30

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2017
Components of Accumulated Other Comprehensive Income, Net of Tax	The tables below present the components of the Company’s AOCI, net of tax (in millions): Pension and Other Postretirement Liabilities Fuel Investments Deferred Total Balance at December 31, 2014 $ (472) $ (499) $ 8 $ (116) $ (1,079) Other comprehensive income (loss) before reclassifications 78 (a) (320) (5) 88 (159) Amounts reclassified from accumulated other comprehensive income 31 604 — (228) 407 Net other comprehensive income (loss) 109 284 (5) (140) 248 Balance at December 31, 2015 $ (363) $ (215) $ 3 $ (256) $ (831) Other comprehensive income (loss) before reclassifications (517) (a) (4) — 187 (334) Amounts reclassified from accumulated other comprehensive income 26 217 (2) 95 336 Net other comprehensive income (loss) (491) 213 (2) 282 2 Balance at December 31, 2016 $ (854) $ (2) $ 1 $ 26 $ (829) Other comprehensive income (loss) before reclassifications (306) (a) — (7) 74 (239) Amounts reclassified from accumulated other comprehensive income 58 2 — (21) 39 Reclassification of stranded tax effects — — — (118) (b) (118) Net other comprehensive income (loss) (248) 2 (7) (65) (318) Balance at December 31, 2017 $ (1,102) $ — $ (6) $ (39) (c) $ (1,147) Details about AOCI Components Amount Reclassified from AOCI to Affected Line Item in Year Ended December 31, 2017 2016 2015 Fuel derivative contracts Fuel contracts-reclassifications of losses into earnings (d) $ 2 $ 217 $ 604 Aircraft fuel Pension and Postretirement liabilities Amortization of unrecognized (gains) losses and prior service cost (e) 58 26 31 Salaries and related costs Investments and other Available-for-sale — (2 ) — Miscellaneous, net (a) Prior service credits increased by $0 million, $30 million and $0 million and actuarial losses increased by approximately $306 million, $560 million and $78 million for 2017, 2016 and 2015, respectively. (b) This amount represents the reclassification from AOCI to RE of the stranded tax effects resulting from the enactment of the Tax Act. (c) Deferred tax balance relates mainly to Pension and Other Postretirement Liabilities. (d) The last of the Company’s fuel hedge derivatives designated for cash flow hedge accounting expired in December 2016. The 2017 amount reclassified from AOCI into fuel expense represents hedge losses on December 2016 settled trades, but for which the associated fuel purchased in December 2016 was not consumed until January 2017. The Company’s current strategy is to not enter into transactions to hedge its fuel consumption, although the Company regularly reviews its strategy based on market conditions and other factors. (e) This AOCI component is included in the computation of net periodic pension and other postretirement costs (see Note 8 of this report for additional information).

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Provision Differed from Amounts Computed at Statutory Federal Income Tax Rate and was Composed of Significant Components	The income tax provision (benefit) differed from amounts computed at the statutory federal income tax rate and consisted of the following significant components, as follows (in millions): UAL 2017 2016 2015 Income tax provision at statutory rate $ 1,050 $ 1,337 $ 1,477 State income taxes, net of federal income tax benefit 29 38 38 Foreign tax rate differential (43) — — Foreign income taxes 3 3 4 Nondeductible employee meals 17 16 15 Impact of Tax Act (192) — — Income tax adjustment from AOCI — 180 — State rate change 12 (12) — Valuation allowance (16) 20 (4,662) Other, net 8 (26) 7 $ 868 $ 1,556 $ (3,121) Current $ (77) $ (92) $ 56 Deferred 945 1,648 (3,177) $ 868 $ 1,556 $ (3,121) United 2017 2016 2015 Income tax provision at statutory rate $ 1,051 $ 1,338 $ 1,477 State income taxes, net of federal income tax 29 38 38 Foreign tax rate differential (43) — — Foreign income taxes 3 3 4 Nondeductible employee meals 17 16 15 Impact of Tax Act (209) — — Income tax adjustment from AOCI — 180 — State rate change 12 (12) — Valuation allowance (16) 20 (4,621) Other, net 8 (25) 7 $ 852 $ 1,558 $ (3,080) Current $ (77) $ (92) $ 56 Deferred 929 1,650 (3,136) $ 852 $ 1,558 $ (3,080)
Components of Deferred Tax Assets and Liabilities	Temporary differences and carryforwards that give rise to deferred tax assets and liabilities at December 31, 2017 and 2016 were as follows (in millions): UAL United 2017 2016 2017 2016 Deferred income tax asset (liability): Federal and state net operating loss (“NOL”) carryforwards $ 601 $ 1,613 $ 574 $ 1,571 Deferred revenue 1,069 2,096 1,069 2,096 Employee benefits, including pension, postretirement and medical 1,051 1,662 1,051 1,662 Alternative minimum tax credit carryforwards — 116 — 116 Other 351 523 351 522 Less: Valuation allowance (63) (68) (63) (68) Total deferred tax assets $ 3,009 $ 5,942 $ 2,982 $ 5,899 Depreciation $ (2,431) $ (3,961) $ (2,431) $ (3,961) Intangibles (803) (1,326) (803) (1,326) Total deferred tax liabilities $ (3,234) $ (5,287) $ (3,234) $ (5,287) Net deferred tax asset (liability) $ (225) $ 655 $ (252) $ 612

Pension and Other Postretirem32

Pension and Other Postretirement Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Reconciliation of Change in Projected Benefit Obligation and Plan Assets	The following table sets forth the reconciliation of the beginning and ending balances of the benefit obligation and plan assets, the funded status and the amounts recognized in these financial statements for the defined benefit and other postretirement plans (in millions): Pension Benefits Year Ended Year Ended Accumulated benefit obligation: $ 4,739 $ 4,158 Change in projected benefit obligation: Projected benefit obligation at beginning of year $ 5,253 $ 4,473 Service cost 195 112 Interest cost 220 200 Actuarial loss 525 738 Gross benefits paid and settlements (366) (243) Other 25 (27) Projected benefit obligation at end of year $ 5,852 $ 5,253 Change in plan assets: Fair value of plan assets at beginning of year $ 3,355 $ 2,975 Actual return on plan assets 510 230 Employer contributions 419 421 Gross benefits paid and settlements (366) (243) Other 14 (28) Fair value of plan assets at end of year $ 3,932 $ 3,355 Funded status—Net amount recognized $ (1,920) $ (1,898) Other Postretirement Benefits Year Ended Year Ended Change in benefit obligation: Benefit obligation at beginning of year $ 1,687 $ 2,002 Service cost 13 19 Interest cost 66 86 Plan participants’ contributions 68 69 Benefits paid (178) (191) Actuarial loss (gain) 40 (165) Plan amendments — (138) Other 14 5 Benefit obligation at end of year $ 1,710 $ 1,687 Change in plan assets: Fair value of plan assets at beginning of year $ 55 $ 56 Actual return on plan assets 1 2 Employer contributions 108 119 Plan participants’ contributions 68 69 Benefits paid (178) (191) Fair value of plan assets at end of year 54 55 Funded status—Net amount recognized $ (1,656) $ (1,632)
Amounts Recognized in Consolidated Balance Sheet and Accumulated Other Comprehensive Income (Loss)	Pension Benefits December 31, 2017 December 31, 2016 Amounts recognized in the consolidated balance sheets consist of: Noncurrent asset $ 9 $ 2 Current liability (8) (8) Noncurrent liability (1,921) (1,892) Total liability $ (1,920) $ (1,898) Amounts recognized in accumulated other comprehensive loss consist of: Net actuarial loss $ (1,610) $ (1,482) Prior service cost (1) (1) Total accumulated other comprehensive loss $ (1,611) $ (1,483) Other Postretirement Benefits December 31, 2017 December 31, 2016 Amounts recognized in the consolidated balance sheets consist of: Current liability $ (54) $ (51) Noncurrent liability (1,602) (1,581) Total liability $ (1,656) $ (1,632) Amounts recognized in accumulated other comprehensive income consist of: Net actuarial gain $ 301 $ 384 Prior service credit 208 245 Total accumulated other comprehensive income $ 509 $ 629
Accumulated Benefit Obligation and Projected Benefit Obligation in Excess of Plan Assets	The following information relates to all pension plans with an accumulated benefit obligation and a projected benefit obligation in excess of plan assets at December 31 (in millions): 2017 2016 Projected benefit obligation $ 5,637 $ 5,025 Accumulated benefit obligation 4,567 3,985 Fair value of plan assets 3,709 3,164
Components Of Net Periodic Benefit Cost	Net periodic benefit cost for the years ended December 31 included the following components (in millions): 2017 2016 2015 Pension Other Pension Other Pension Other Service cost $ 195 $ 13 $ 112 $ 19 $ 124 $ 21 Interest cost 220 66 200 86 200 82 Expected return on plan assets (243) (2) (216) (2) (194) (2) Curtailment gain — — — (107) — — Amortization of unrecognized actuarial (gain) loss 128 (33) 76 (19) 85 (22) Amortization of prior service credits — (37) — (31) — (32) Other 5 — 5 — 4 — Net periodic benefit cost (credit) $ 305 $ 7 $ 177 $ (54) $ 219 $ 47
Amortized Accumulated Other Comprehensive Income (Loss) Into Net Periodic Benefit Cost	The estimated amounts that will be amortized in 2018 out of accumulated other comprehensive income (loss) into net periodic benefit cost are as follows (in millions): Pension Benefits Other Actuarial (gain) loss $ 132 $ (32) Prior service (credit) cost — (37)
Assumptions Used for Benefit Plans	The assumptions used for the benefit plans were as follows: Pension Benefits Assumptions used to determine benefit obligations 2017 2016 Discount rate 3.65% 4.18% Rate of compensation increase 3.89% 3.54% Assumptions used to determine net expense Discount rate 4.19% 4.58% Expected return on plan assets 7.02% 7.04% Rate of compensation increase 3.54% 3.53% Other Postretirement Benefits Assumptions used to determine benefit obligations 2017 2016 Discount rate 3.63% 4.07% Assumptions used to determine net expense Discount rate 4.07% 4.49% Expected return on plan assets 3.00% 3.00% Health care cost trend rate assumed for next year 6.25% 6.50% Rate to which the cost trend rate is assumed to decline (ultimate trend rate in 2023) 5.00% 5.00%
Allocation of Plan Assets	United’s plan assets are allocated within the following guidelines: Percent of Total Expected Long-Term Rate of Return Equity securities 27-42 % 9.5 % Fixed-income securities 30-40 5.5 Alternatives 10-25 7.3 Other 0-10 7.3
Effect of One-Percentage-Point Change in Assumed Health Care Trend Rate	A 1% change in the assumed health care trend rate for the Company would have the following additional effects (in millions): 1% Increase 1% Decrease Effect on total service and interest cost for the year ended December 31, 2017 $ 11 $ (8) Effect on postretirement benefit obligation at December 31, 2017 170 (149)
Pension and Other Postretirement Plan Assets	The following tables present information about United’s pension and other postretirement plan assets at December 31 (in millions): 2017 2016 Pension Plan Assets: Total Level 1 Level 2 Level 3 Assets Total Level 1 Level 2 Level 3 Assets Equity securities funds $ 1,406 $ 269 $ 133 $ — $ 1,004 $ 1,173 $ 230 $ 111 $ — $ 832 Fixed-income securities 1,470 — 834 18 618 1,298 — 824 11 463 Alternatives 637 — — 139 498 586 — — 134 452 Other investments 419 32 124 172 91 298 47 68 87 96 Total $ 3,932 $ 301 $ 1,091 $ 329 $ 2,211 $ 3,355 $ 277 $ 1,003 $ 232 $ 1,843 Other Postretirement Benefit Plan Assets: Deposit administration fund $ 54 $ — $ — $ 54 $ — $ 55 $ — $ — $ 55 $ — (a) In accordance with the relevant accounting standards, certain investments that are measured at fair value using the net asset value (“NAV”) per share (or its equivalent) have not been classified in the fair value hierarchy. These investments are commingled funds that invest in fixed-income instruments including bonds, debt securities, and other similar instruments issued by various U.S. and non-U.S.
Defined Benefit Plan Assets Measured at Fair Value Using Unobservable Inputs (Level Three)	The reconciliation of United’s defined benefit plan assets measured at fair value using unobservable inputs (Level 3) for the years ended December 31, 2017 and 2016 is as follows (in millions): 2017 2016 Balance at beginning of year $ 287 $ 208 Actual return on plan assets: Sold during the year 7 4 Held at year end 16 3 Purchases, sales, issuances and settlements (net) 73 72 Balance at end of year $ 383 $ 287
Estimated Future Benefit Payments	The estimated future benefit payments, net of expected participant contributions, in United’s pension plans and other postretirement benefit plans as of December 31, 2017 are as follows (in millions): Pension Other Postretirement Other Postretirement— subsidy receipts 2018 $ 305 $ 113 $ 6 2019 326 118 6 2020 331 121 6 2021 357 124 7 2022 369 126 7 Years 2023 – 2027 1,912 646 43
Multi-Employer Plans	Pension Fund IAM National Pension Fund EIN/ Pension Plan Number 51-6031295 - 002 Pension Protection Act Zone Status (2017 and 2016) Green Zone. Plans in the green zone are at least 80 percent funded. FIP/RP Status Pending/Implemented No United’s Contributions $50 million, $41 million and $40 million in the years ended December 31, 2017, 2016 and 2015, respectively Surcharge Imposed No Expiration Date of Collective Bargaining Agreement N/A

Fair Value Measurements and I33

Fair Value Measurements and Investments (Tables)	12 Months Ended
	Dec. 31, 2017
Financial Assets and Liabilities Measured at Fair Value on Recurring Basis	The table below presents disclosures about the fair value of financial assets and liabilities measured at fair value on a recurring basis in the Company’s financial statements as of December 31 (in millions): 2017 2016 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Cash and cash equivalents $ 1,482 $ 1,482 $ — $ — $ 2,179 $ 2,179 $ — $ — Short-term investments: Corporate debt 958 — 958 — 835 — 835 — Asset-backed securities 753 — 753 — 792 — 792 — Certificates of deposit placed through an account registry service (“CDARS”) 120 — 120 — 246 — 246 — U.S. government and agency notes 113 — 113 — 140 — 140 — Other fixed-income securities 188 — 188 — 54 — 54 — Other investments measured at NAV 184 — — — 182 — — — Restricted cash 109 109 — — 124 124 — — Long-term investments: Equity securities 99 99 — — — — — — Enhanced equipment trust certificates (“EETC”) 22 — — 22 23 — — 23
Carrying Values and Estimated Fair Values of Financial Instruments	The table below presents the carrying values and estimated fair values of financial instruments not presented in the tables above as of December 31 (in millions): Fair Value of Debt by Fair Value Hierarchy Level 2017 2016 Carrying Fair Value Carrying Fair Value Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Long-term debt $ 13,268 $ 13,787 $ — $ 10,115 $ 3,672 $ 10,767 $ 11,055 $ — $ 8,184 $ 2,871

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt	(In millions) At December 31, 2017 2016 Secured Notes payable, fixed interest rates of 2.88% to 9.52% (weighted average rate of 4.39% as of December 31, 2017), payable through 2028 $ 8,661 $ 7,586 Notes payable, floating interest rates of the London interbank offered rate (“LIBOR”) plus 0.2% to 2.25%, payable through 2028 1,880 1,546 Term loan, LIBOR plus 2.00%, or alternative rate based on certain market rates plus 1.00%, due 2024 1,489 — Term loan, LIBOR subject to a 0.75% floor, plus 2.50%, or alternative rate based on certain market rates plus 1.50%, due 2019 — 866 Term loan, LIBOR subject to a 0.75% floor, plus 2.75%, or alternative rate based on certain market rates plus 1.75%, due 2021 — 192 Unsecured 6.375% Senior Notes due 2018 (a) 300 300 6% Senior Notes due 2020 (a) 300 300 4.25% Senior Notes due 2022 (a) 400 — 5% Senior Notes due 2024 (a) 300 — Other 101 101 13,431 10,891 Less: unamortized debt discount, premiums and debt issuance costs (163) (124) Less: current portion of long-term debt (1,565) (849) Long-term debt, net $ 11,703 $ 9,918 (a) UAL is the issuer of this debt. United is a guarantor.
Contractual Principal Payments	The table below presents the Company’s contractual principal payments (not including debt discount or debt issuance costs) at December 31, 2017 under then-outstanding long-term debt agreements in each of the next five calendar years (in millions): 2018 $ 1,565 2019 1,165 2020 1,170 2021 1,157 2022 1,492 After 2022 6,882 $ 13,431
Details of Pass Through Trusts	Certain details of the pass-through trusts with proceeds received from issuance of debt in 2017 are as follows (in millions, except stated interest rate): EETC Date Class Principal Final expected Stated Total debt recorded Proceeds Remaining February 2018 AA $ 677 March 2030 3.50% $ — $ — $ 677 February 2018 A 258 March 2030 3.70% — — 258 November 2017 B 258 January 2026 3.65% 258 258 — November 2017 B 236 October 2025 3.65% 236 236 — September 2016 AA 637 October 2028 2.875% 637 557 — September 2016 A 283 October 2028 3.10% 283 247 — June 2016 AA 729 July 2028 3.10% 729 319 — June 2016 A 324 July 2028 3.45% 324 142 — $ 3,402 $ 2,467 $ 1,759 $ 935
Summary of Collateral Covenants and Cross Default Provisions	The collateral, covenants and cross default provisions of the Company’s principal debt instruments that contain such provisions are summarized in the table below: Debt Instrument Collateral, Covenants and Cross Default Provisions Various equipment notes and other notes payable Secured by certain aircraft. The indentures contain events of default that are customary for aircraft financing, including in certain cases cross default to other related aircraft. Credit Agreement Secured by certain of United’s international route authorities, specified take-off The 2017 Credit Agreement requires the Company to maintain at least $2.0 billion of unrestricted liquidity at all times, which includes unrestricted cash, short-term investments and any undrawn amounts under any revolving credit facility, and to maintain a minimum ratio of appraised value of collateral to the outstanding obligations under the 2017 Credit Agreement of 1.6 to 1.0 at all times. The 2017 Credit Agreement contains covenants that, among other things, restrict the ability of UAL and its restricted subsidiaries (as defined in the 2017 Credit Agreement) to incur additional indebtedness and to pay dividends on or repurchase stock, although the Company currently has ample ability under these restrictions to repurchase stock under the Company’s share repurchase program. The 2017 Credit Agreement contains events of default customary for this type of financing, including a cross default and cross acceleration provision to certain other material indebtedness of the Company. 6.375% Senior Notes due 2018 6% Senior Notes due 2020 4.25% Senior Notes due 2022 5% Senior Notes due 2024 The indentures for these notes contain covenants that, among other things, restrict the ability of the Company and its restricted subsidiaries (as defined in the indentures) to incur additional indebtedness and pay dividends on or repurchase stock, although the Company currently has ample ability under these restrictions to repurchase stock under the Company’s share repurchase program.

Leases and Capacity Purchase 35

Leases and Capacity Purchase Agreements (Tables)	12 Months Ended
	Dec. 31, 2017
Future Minimum Lease Payments for Capital and Operating Leases	At December 31, 2017, United’s scheduled future minimum lease payments under operating leases having initial or remaining noncancelable lease terms of more than one year, aircraft leases, including aircraft rent under CPAs and capital leases (substantially all of which are for aircraft) were as follows (in millions): Capital Leases (a) Facility and Other Aircraft Operating 2018 $ 200 $ 1,234 $ 1,038 2019 133 1,075 855 2020 113 1,169 628 2021 110 935 510 2022 105 797 388 After 2022 1,156 6,109 1,513 Minimum lease payments $ 1,817 $ 11,319 $ 4,932 Imputed interest (693) Present value of minimum lease payments 1,124 Current portion (128) Long-term obligations under capital leases $ 996 (a) Includes airport construction projects managed by United in which United has construction risk, including project cost overruns. The Company recorded an asset for project costs and a related liability equal to project costs funded by parties other than United. As of December 31, 2017, United had an asset balance of $814 million recorded in operating property and equipment and $777 million recorded in current and long-term obligations under capital leases for these airport construction projects.
Future Lease Payment Under Terms of Capacity Purchase Agreement	Based on these assumptions as of December 31, 2017, our future payments through the end of the terms of our CPAs are presented in the table below (in billions): 2018 $ 2.0 2019 1.8 2020 1.6 2021 1.5 2022 1.4 After 2022 3.2 $ 11.5

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	12 Months Ended
	Dec. 31, 2017
Schedule of Commitments to Purchase Aircrafts	The table below summarizes United’s commitments as of December 31, 2017, which primarily relate to the acquisition of aircraft and related spare engines, aircraft improvements and include other capital purchase commitments for the years ended December 31 (in billions). Any new firm aircraft orders, including through the exercise of purchase options and purchase rights, will increase the total future capital commitments of the Company. 2018 $ 3.2 2019 2.9 2020 2.1 2021 2.4 2022 1.8 After 2022 9.8 $ 22.2
Aircraft Type
Schedule of Commitments to Purchase Aircrafts	As of December 31, 2017, United had firm commitments and options to purchase aircraft from The Boeing Company (“Boeing”) and Airbus presented in the table below: Aircraft Type Number of Firm Airbus A350 45 Boeing 737 MAX 161 Boeing 777-300ER 4 Boeing 787 18 (a) United also has options and purchase rights for additional aircraft.

SPECIAL CHARGES (Tables)

SPECIAL CHARGES (Tables)	12 Months Ended
	Dec. 31, 2017
Components of Special charges	Special charges in the statements of consolidated operations consisted of the following for the years ended December 31 (in millions): Operating: 2017 2016 2015 Severance and benefit costs $ 116 $ 37 $ 107 Impairment of assets 25 412 79 Cleveland airport lease restructuring — 74 — Labor agreement costs — 64 18 (Gains) losses on sale of assets and other special charges 35 51 122 Total operating special charges 176 638 326 Nonoperating: (Gains) losses on extinguishment of debt and other — (1) 202 Total operating and nonoperating special charges before income taxes 176 637 528 Income tax benefit related to special charges (63) (229) (11) Income tax adjustments (Notes 6 and 7) (192) 180 (3,130) Total operating and nonoperating special charges, net of income taxes and income tax adjustments $ (79) $ 588 $ (2,613)
Accrual Activity	Activity related to the accruals for severance and medical costs and future lease payments on permanently grounded aircraft is as follows (in millions): Severance/ Permanently Balance at December 31, 2014 $ 109 $ 102 Accrual 107 30 Payments (189) (54) Balance at December 31, 2015 27 78 Accrual and related adjustments 37 (17) Payments (50) (20) Balance at December 31, 2016 14 41 Accrual 116 (4) Payments (93) (15) Balance at December 31, 2017 $ 37 $ 22

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	12 Months Ended
	Dec. 31, 2017
Operating Revenue by Principle Geographic Region	The Company’s operating revenue by principal geographic region (as defined by the U.S. Department of Transportation) for the years ended December 31 is presented in the table below (in millions): 2017 2016 2015 Domestic (U.S. and Canada) $ 23,131 $ 22,202 $ 21,931 Pacific 4,898 4,959 5,498 Atlantic 6,285 6,157 7,068 Latin America 3,422 3,238 3,367 Total $ 37,736 $ 36,556 $ 37,864

SELECTED QUARTERLY FINANCIAL 39

SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) (Tables)	12 Months Ended
	Dec. 31, 2017
Schedule of Selected Quarterly Financial Data	UAL Quarter Ended (In millions, except per share amounts) March 31 June 30 September 30 December 31 2017 Operating revenue $ 8,420 $ 10,000 $ 9,878 $ 9,438 Income from operations 278 1,399 1,092 729 Net income 96 818 637 580 Basic earnings per share 0.31 2.67 2.12 1.99 Diluted earnings per share 0.31 2.66 2.12 1.99 2016 Operating revenue $ 8,195 $ 9,396 $ 9,913 $ 9,052 Income from operations 649 1,060 1,624 1,005 Net income 313 588 965 397 Basic earnings per share 0.88 1.78 3.02 1.26 Diluted earnings per share 0.88 1.78 3.01 1.26
Schedule of Effect of Four Quarters Events	UAL’s quarterly financial data is subject to seasonal fluctuations and historically its second and third quarter financial results, which reflect higher travel demand, are better than its first and fourth quarter financial results. UAL’s quarterly results were impacted by the following significant items (in millions): Quarter Ended March 31 June 30 September 30 December 31 2017 Operating: Severance and benefit costs $ 37 $ 41 $ 23 $ 15 Impairment of assets — — 15 10 (Gains) losses on sale of assets and other special charges 14 3 12 6 Total operating special charges 51 44 50 31 Income taxes: Income tax benefit related to special charges (18) (16) (18) (11) Income tax adjustments (Note 7) — — — (192) Total operating special charges, net of income taxes and income tax adjustments $ 33 $ 28 $ 32 $ (172) 2016 Operating: Labor agreement costs and related items $ 100 $ 10 $ 14 $ (60) Cleveland airport lease restructuring 74 — — — Severance and benefit costs 8 6 13 10 Impairment of assets — 412 — — (Gains) losses on sale of assets and other special charges 8 6 18 19 Total operating special charges 190 434 45 (31) Nonoperating and income taxes: Losses (gain) on extinguishment of debt and other 8 (9) — — Income tax expense (benefit) related to special charges (72) (153) (16) 12 Income tax adjustments (Note 6) — — — 180 Total operating and nonoperating special charges, net of income taxes and income tax adjustments $ 126 $ 272 $ 29 $ 161

Significant Accounting Polici40

Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary Of Significant Accounting Policies [Line Items]
Residual value	10.00%
Carrying value of computer software	$ 345	$ 356
Advertising expense	217	220	$ 201
ASU 2018-02
Summary Of Significant Accounting Policies [Line Items]
Tax Cuts and Jobs Act of 2017, reclassification from AOCI to retained earnings, tax effect	$ 118
Minimum
Summary Of Significant Accounting Policies [Line Items]
Refundable tickets expiration period	1 year
Computer software
Summary Of Significant Accounting Policies [Line Items]
Depreciation expense related to computer software	$ 117	$ 108	$ 93
Aircraft and aircraft spare parts
Summary Of Significant Accounting Policies [Line Items]
Residual value	10.00%

Schedule of Information Related

Schedule of Information Related to Amounts Recorded Related to Frequent Flyer Program (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Significant Accounting Policies [Line Items]
Cash Proceeds from Miles Sold and Earned		$ 2,343	$ 3,022	$ 2,999
Other Revenue Recognized Upon Award of Miles to Third-Party Customers	[1]	1,183	1,221	1,050
Increase in Frequent Flyer Deferred Revenue for Miles Awarded	[2]	2,025	2,050	2,173
Decrease in Advanced Purchase of Miles	[3]	$ (865)	$ (249)	$ (224)
[1]	This amount represents other revenue recognized during the period from the sale of miles to third parties, representing the marketing-related deliverable services component of the sale.
[2]	This amount represents the increase to Frequent flyer deferred revenue during the period.
[3]	This amount represents the net decrease in the advance purchase of miles obligation due to cash payments for the sale of miles less than miles awarded to customers.

Schedule of Cash and Cash Equiv

Schedule of Cash and Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 1,482	$ 2,179	$ 3,006
Other assets:
Restricted cash	91	124	204
Total cash, cash equivalents and restricted cash shown in the statement of consolidated cash flows	1,591	2,303	3,212	$ 2,322
Prepaid Expenses and Other
Current assets:
Restricted cash	18		2
United Airlines, Inc.
Current assets:
Cash and cash equivalents	1,476	2,173	3,000
Other assets:
Restricted cash	91	124	204
Total cash, cash equivalents and restricted cash shown in the statement of consolidated cash flows	1,585	$ 2,297	3,206	$ 2,316
United Airlines, Inc. | Prepaid Expenses and Other
Current assets:
Restricted cash	$ 18		$ 2

Estimated Useful Lives of Prope

Estimated Useful Lives of Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2017
Aircraft and related rotable parts | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	25 years
Aircraft and related rotable parts | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	30 years
Buildings | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	25 years
Buildings | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	45 years
Other property and equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	3 years
Other property and equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	15 years
Computer software | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	5 years
Computer software | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	15 years
Building improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	1 year
Building improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	40 years

Schedule of Adoption of ASC 606

Schedule of Adoption of ASC 606 and Expected Impact - Statements of Consolidated Operations (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating revenue:
Passenger-Mainline									$ 26,552	$ 25,414	$ 26,333
Passenger-Regional									5,852	6,043	6,452
Total passenger revenue									32,404	31,457	32,785
Cargo									1,035	876	937
Other operating revenue									4,297	4,223	4,142
Total operating revenue	$ 9,438	$ 9,878	$ 10,000	$ 8,420	$ 9,052	$ 9,913	$ 9,396	$ 8,195	37,736	36,556	37,864
Operating expenses									34,238	32,218	32,698
Operating income	729	1,092	1,399	278	1,005	1,624	1,060	649	3,498	4,338	5,166
Nonoperating expense, net									(499)	(519)	(947)
Income before income taxes									2,999	3,819	4,219
Income tax expense (benefit)									868	1,556	(3,121)
Net income	$ 580	$ 637	$ 818	$ 96	$ 397	$ 965	$ 588	$ 313	$ 2,131	$ 2,263	$ 7,340
Earnings per share, basic	$ 1.99	$ 2.12	$ 2.67	$ 0.31	$ 1.26	$ 3.02	$ 1.78	$ 0.88	$ 7.04	$ 6.86	$ 19.52
Earnings per share, diluted	$ 1.99	$ 2.12	$ 2.66	$ 0.31	$ 1.26	$ 3.01	$ 1.78	$ 0.88	$ 7.02	$ 6.85	$ 19.47
Operating expense:
Salaries and related costs									$ 11,045	$ 10,275	$ 9,713
Special charges	$ 31	$ 50	$ 44	$ 51	$ (31)	$ 45	$ 434	$ 190	176	638	326
Nonoperating income (expense):
Miscellaneous, net									3	(19)	$ (352)
ASC 606
Operating revenue:
Passenger-Mainline									28,259	27,029
Passenger-Regional									6,201	6,400
Total passenger revenue									34,460	33,429
Cargo									1,114	934
Other operating revenue									2,210	2,195
Total operating revenue									37,784	36,558
Operating expenses									34,217	32,206
Operating income									3,567	4,352
Nonoperating expense, net									(527)	(579)
Income before income taxes									3,040	3,773
Income tax expense (benefit)									896	1,539
Net income									$ 2,144	$ 2,234
Earnings per share, basic									$ 7.08	$ 6.77
Earnings per share, diluted									$ 7.06	$ 6.76
ASU 2017-07
Operating expense:
Salaries and related costs									$ 10,941	$ 10,176
Special charges									176	745
Nonoperating income (expense):
Miscellaneous, net									(101)	(11)
Scenario, Previously Reported | ASC 606
Operating revenue:
Passenger-Mainline									26,552	25,414
Passenger-Regional									5,852	6,043
Total passenger revenue									32,404	31,457
Cargo									1,035	876
Other operating revenue									4,297	4,223
Total operating revenue									37,736	36,556
Operating expenses									34,238	32,218
Operating income									3,498	4,338
Nonoperating expense, net									(499)	(519)
Income before income taxes									2,999	3,819
Income tax expense (benefit)									868	1,556
Net income									$ 2,131	$ 2,263
Earnings per share, basic									$ 7.04	$ 6.86
Earnings per share, diluted									$ 7.02	$ 6.85
Scenario, Previously Reported | ASU 2017-07
Operating expense:
Salaries and related costs									$ 11,045	$ 10,275
Special charges									176	638
Nonoperating income (expense):
Miscellaneous, net									3	(19)
Adjustment | ASC 606
Operating revenue:
Passenger-Mainline									1,707	1,615
Passenger-Regional									349	357
Total passenger revenue									2,056	1,972
Cargo									79	58
Other operating revenue									(2,087)	(2,028)
Total operating revenue									48	2
Operating expenses									(21)	(12)
Operating income									69	14
Nonoperating expense, net									(28)	(60)
Income before income taxes									41	(46)
Income tax expense (benefit)									28	(17)
Net income									$ 13	$ (29)
Earnings per share, basic									$ 0.04	$ (0.09)
Earnings per share, diluted									$ 0.04	$ (0.09)
Adjustment | ASU 2017-07
Operating expense:
Salaries and related costs									$ (104)	$ (99)
Special charges										107
Nonoperating income (expense):
Miscellaneous, net									$ (104)	$ 8

Schedule of Adoption of ASC 645

Schedule of Adoption of ASC 606 and Expected Impact - Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Prepaid expenses and other	$ 1,051	$ 832
Other assets:
Deferred income taxes		655
Current liabilities:
Advance ticket sales	3,876	3,730
Frequent flyer deferred revenue	2,176	2,135
Other	569	1,010
Other liabilities and deferred credits:
Frequent flyer deferred revenue	2,565	2,748
Advanced purchase of miles		430
Deferred income taxes	225
Stockholders' equity:
Retained earnings	4,621	3,427
ASC 606
Current assets:
Prepaid expenses and other	1,071	852
Other assets:
Deferred income taxes		703
Current liabilities:
Advance ticket sales	3,940	3,795
Frequent flyer deferred revenue	2,192	2,149
Other	576	1,089
Other liabilities and deferred credits:
Frequent flyer deferred revenue	2,591	2,740
Advanced purchase of miles		433
Deferred income taxes	204
Stockholders' equity:
Retained earnings	4,549	3,342
Scenario, Previously Reported | ASC 606
Current assets:
Prepaid expenses and other	1,051	832
Other assets:
Deferred income taxes		655
Current liabilities:
Advance ticket sales	3,876	3,730
Frequent flyer deferred revenue	2,176	2,135
Other	569	1,010
Other liabilities and deferred credits:
Frequent flyer deferred revenue	2,565	2,748
Advanced purchase of miles		430
Deferred income taxes	225
Stockholders' equity:
Retained earnings	4,621	3,427
Adjustment | ASC 606
Current assets:
Prepaid expenses and other	20	20
Other assets:
Deferred income taxes		48
Current liabilities:
Advance ticket sales	64	65
Frequent flyer deferred revenue	16	14
Other	7	79
Other liabilities and deferred credits:
Frequent flyer deferred revenue	26	(8)
Advanced purchase of miles		3
Deferred income taxes	(21)
Stockholders' equity:
Retained earnings	$ (72)	$ (85)

Goodwill and Other Intangible46

Goodwill and Other Intangible Assets (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Goodwill And Intangible Assets [Line Items]
Goodwill		$ 4,523	$ 4,523
Finite-lived intangible assets, Gross Carrying Amount		1,757	1,771
Finite-lived intangible assets, Accumulated Amortization		1,313	1,234
Indefinite-lived intangible assets, Gross Carrying Amount		$ 3,095	3,095
Frequent Flyer Database
Goodwill And Intangible Assets [Line Items]
Asset life	[1],[2]	22 years
Finite-lived intangible assets, Gross Carrying Amount	[1]	$ 1,177	1,177
Finite-lived intangible assets, Accumulated Amortization	[1]	$ 832	771
Hubs
Goodwill And Intangible Assets [Line Items]
Asset life	[2]	20 years
Finite-lived intangible assets, Gross Carrying Amount		$ 145	145
Finite-lived intangible assets, Accumulated Amortization		$ 89	82
Contracts
Goodwill And Intangible Assets [Line Items]
Asset life	[2]	13 years
Finite-lived intangible assets, Gross Carrying Amount		$ 121	135
Finite-lived intangible assets, Accumulated Amortization		$ 103	95
Patents And Trade Names
Goodwill And Intangible Assets [Line Items]
Asset life	[2]	3 years
Finite-lived intangible assets, Gross Carrying Amount		$ 108	108
Finite-lived intangible assets, Accumulated Amortization		$ 108	108
Airport Slots and Gates
Goodwill And Intangible Assets [Line Items]
Asset life	[2]	8 years
Finite-lived intangible assets, Gross Carrying Amount		$ 97	97
Finite-lived intangible assets, Accumulated Amortization		$ 97	97
Other Intangible Assets
Goodwill And Intangible Assets [Line Items]
Asset life	[2]	25 years
Finite-lived intangible assets, Gross Carrying Amount		$ 109	109
Finite-lived intangible assets, Accumulated Amortization		84	81
Route Authorities
Goodwill And Intangible Assets [Line Items]
Indefinite-lived intangible assets, Gross Carrying Amount		1,562	1,562
Airport Slots And Gates
Goodwill And Intangible Assets [Line Items]
Indefinite-lived intangible assets, Gross Carrying Amount		536	536
Tradenames And Logos
Goodwill And Intangible Assets [Line Items]
Indefinite-lived intangible assets, Gross Carrying Amount		593	593
Alliances
Goodwill And Intangible Assets [Line Items]
Indefinite-lived intangible assets, Gross Carrying Amount		$ 404	$ 404
[1]	The frequent flyer database is amortized based on an accelerated amortization schedule to reflect utilization of the assets. Estimated cash flows correlating to the expected attrition rate of customers in the frequent flyer database is considered in the determination of the amortization schedules.
[2]	Weighted average life expressed in years.

Goodwill and Other Intangible47

Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Actual and Estimated Amortization Expense [Line Items]
Actual amortization	$ 79	$ 90	$ 105
Projected amortization in 2018	67
Projected amortization in 2019	61
Projected amortization in 2020	55
Projected amortization in 2021	50
Projected amortization in 2022	$ 40

Common Stockholders' Equity a48

Common Stockholders' Equity and Preferred Securities - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Stockholders Equity [Line Items]
Number of shares repurchased	28,000,000
Repurchases of common stock	$ 1,844	$ 2,607	$ 1,232
Share repurchase program additional amount authorized	3,000
Amount remaining under repurchase programs	$ 3,000
Treasury stock, shares, retired	25,000,000
Treasury stock retired, average cost per share	$ 63
Common stock reserved for future issuance	10,000,000
Junior preferred stock outstanding	2
Junior preferred stock par value per share	$ 0.01
Preferred stock authorized to issue	250,000,000

Computation of Earnings Per Sha

Computation of Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Computation of Earnings Per Share [Line Items]
Earnings available to common stockholders									$ 2,131	$ 2,263	$ 7,340
Basic weighted-average shares outstanding									302.7	329.9	376.1
Effect of convertible notes											0.3
Effect of employee stock awards									0.9	0.4	0.5
Diluted weighted-average shares outstanding									303.6	330.3	376.9
Earnings per share, basic	$ 1.99	$ 2.12	$ 2.67	$ 0.31	$ 1.26	$ 3.02	$ 1.78	$ 0.88	$ 7.04	$ 6.86	$ 19.52
Earnings per share, diluted	$ 1.99	$ 2.12	$ 2.66	$ 0.31	$ 1.26	$ 3.01	$ 1.78	$ 0.88	$ 7.02	$ 6.85	$ 19.47

Share-Based Compensation Plan50

Share-Based Compensation Plans - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity awards fair value	$ 76	$ 80	$ 92
Outstanding stock option awards	500,000
Outstanding stock option awards, exercisable	100,000
Outstanding weighted average exercise price	$ 51.67
Outstanding exercisable weighted average exercise price	$ 34.74
Outstanding intrinsic value	$ 8
Outstanding exercisable intrinsic value	$ 5
Outstanding weighted average remaining contractual live	6 years 3 months 19 days
Outstanding exercisable weighted average remaining contractual live	3 years 8 months 12 days
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, other than options, awards granted	1,600,000	1,900,000	1,000,000
Liabilities related to share based payments	$ 38
Payment related to share-based liabilities	$ 50	$ 69	$ 85
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, options, awards granted	36,000
Share-Based Compensation, options term	10 years
Percentage of premium of the grant date fair market value		25.00%
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 77.56	$ 56.19
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, grant date fair value	$ 0.7	$ 2.3
Stock Options | Exercise Prices Equal to Fair Market Value
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, options, awards granted	36,000	100,000	0
Stock Options | Stock options with exercise prices at a 25% premium of the grant date fair market value
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, options, awards granted		300,000
Time-Vested RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, other than options, awards granted	1,000,000
Share-Based Compensation, vesting period	3 years
Number of days used to compute performance period average closing price of restricted stock units	20 days
Performance-Based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, other than options, awards granted	600,000
Share-Based Compensation, vesting period	3 years
Number of days used to compute performance period average closing price of restricted stock units	20 days
Share-Based Compensation, vesting date	Dec. 31, 2019

Schedule of Share-Based Compens

Schedule of Share-Based Compensation Plan Cost (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	$ 73	$ 70	$ 58
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	63	58	52
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	8	11	$ 6
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	$ 2	$ 1

Schedule of Unearned Compensati

Schedule of Unearned Compensation and Weighted Average Remaining Period for Outstanding Share-Based Awards (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unearned Compensation	$ 53
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unearned Compensation	$ 46
Weighted- Average Remaining Period (in years)	1 year 10 months 25 days
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unearned Compensation	$ 4
Weighted- Average Remaining Period (in years)	3 years 10 months 25 days
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unearned Compensation	$ 3
Weighted- Average Remaining Period (in years)	1 year 2 months 12 days

Schedule of Restricted Stock Un

Schedule of Restricted Stock Unit and Restricted Stock Activity (Detail) - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding at beginning of year	0.5	0.3	0.7
Granted, Stock		0.4	0.2
Vested, Stock	(0.2)	(0.1)	(0.4)
Forfeited, Stock		(0.1)	(0.2)
Outstanding at end of year, Stock	0.3	0.5	0.3
Weighted-Average Grant Price at beginning of year	$ 52	$ 48.68	$ 32.55
Granted, Weighted-Average Grant Price		50.63	66.53
Vested, Weighted-Average Grant Price	51.60	41.47	31.14
Forfeited, Weighted-Average Grant Price	51.88	53.42	46.23
Outstanding at end of year, Weighted-Average Grant Price	$ 52.30	$ 52	$ 48.68
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding at beginning of year	2.9	2.6	3.8
Granted, Stock	1.6	1.9	1
Vested, Stock	(1)	(1.4)	(1.6)
Forfeited, Stock	(0.3)	(0.2)	(0.6)
Outstanding at end of year, Stock	3.2	2.9	2.6

Components of Accumulated Other

Components of Accumulated Other Comprehensive Income, Net of Tax (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, deferred taxes		$ 26		$ (256)	$ (116)
Other comprehensive income (loss) before reclassifications, deferred taxes		74		187	88
Amounts reclassified from accumulated other comprehensive income, deferred taxes		(21)		95	(228)
Reclassification of stranded tax effects	[1]	(118)
Net other comprehensive income (loss), deferred taxes		(65)		282	(140)
Ending Balance, deferred taxes		(39)	[2]	26	(256)
Beginning Balance		8,659		8,966	2,396
Other comprehensive income (loss) before reclassifications, net of tax		(239)		(334)	(159)
Amounts reclassified from accumulated other comprehensive income, net of tax		39		336	407
Total other comprehensive income (loss), net		(318)		2	248
Ending Balance		8,806		8,659	8,966
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(829)		(831)	(1,079)
Reclassification of stranded tax effects		(118)
Ending Balance		(1,147)		(829)	(831)
Pension and Other Postretirement Liabilities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, before tax		(854)		(363)	(472)
Other comprehensive income (loss) before reclassifications, before tax	[3]	(306)		(517)	78
Amounts reclassified from accumulated other comprehensive income, before tax		58		26	31
Net other comprehensive income (loss), before tax		(248)		(491)	109
Ending Balance, before tax		(1,102)		(854)	(363)
Derivative Contracts | Fuel
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, before tax		(2)		(215)	(499)
Other comprehensive income (loss) before reclassifications, before tax				(4)	(320)
Amounts reclassified from accumulated other comprehensive income, before tax		2		217	604
Net other comprehensive income (loss), before tax		2		213	284
Ending Balance, before tax				(2)	(215)
Investments and Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, before tax		1		3	8
Other comprehensive income (loss) before reclassifications, before tax		(7)			(5)
Amounts reclassified from accumulated other comprehensive income, before tax				(2)
Net other comprehensive income (loss), before tax		(7)		(2)	(5)
Ending Balance, before tax		$ (6)		$ 1	$ 3
[1]	This amount represents the reclassification from AOCI to RE of the stranded tax effects resulting from the enactment of the Tax Act.
[2]	Deferred tax balance relates mainly to Pension and Other Postretirement Liabilities.
[3]	Prior service credits increased by $0 million, $30 million and $0 million and actuarial losses increased by approximately $306 million, $560 million and $78 million for 2017, 2016 and 2015, respectively.

Details about Accumulated Other

Details about Accumulated Other Comprehensive Income Components (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Salaries And Related Costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortization of unrecognized (gains) losses and prior service cost and the effect of curtailments and settlements	[1]	$ 58	$ 26	$ 31
Miscellaneous, Net
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassifications of gains into earnings			(2)
Fuel Oil Contract | Aircraft Fuel
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassifications of losses into earnings	[2]	$ 2	$ 217	$ 604
[1]	This AOCI component is included in the computation of net periodic pension and other postretirement costs (see Note 8 of this report for additional information).
[2]	The last of the Company's fuel hedge derivatives designated for cash flow hedge accounting expired in December 2016. The 2017 amount reclassified from AOCI into fuel expense represents hedge losses on December 2016 settled trades, but for which the associated fuel purchased in December 2016 was not consumed until January 2017. The Company's current strategy is to not enter into transactions to hedge its fuel consumption, although the Company regularly reviews its strategy based on market conditions and other factors.

Components of Accumulated Oth56

Components of Accumulated Other Comprehensive Income, Net of Tax (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Increase in prior service credits	$ 0	$ 30	$ 0
Increase in actuarial losses	$ 306	$ 560	$ 78

Accumulated Other Comprehensi57

Accumulated Other Comprehensive Income (Loss) - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Sep. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Valuation allowance	$ 68	$ 63
Income tax adjustment from AOCI	$ 180
Valuation allowance for deferred tax assets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Valuation allowance			$ 465
Pension and Other Postretirement Liabilities | Valuation allowance for deferred tax assets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Valuation allowance			285
Fuel | Designated as Hedging Instrument | Valuation allowance for deferred tax assets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Valuation allowance			$ 180

Income Tax Provision Differed f

Income Tax Provision Differed from Amounts Computed at Statutory Federal Income Tax Rate and Significant Components (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Income tax provision at statutory rate	$ 1,050	$ 1,337	$ 1,477
State income taxes, net of federal income tax	29	38	38
Foreign tax rate differential	(43)
Foreign income taxes	3	3	4
Nondeductible employee meals	17	16	15
Impact of Tax Act	(192)
Income tax adjustment from AOCI		180
State rate change	12	(12)
Valuation allowance	(16)	20	(4,662)
Other, net	8	(26)	7
Income tax expense (benefit)	868	1,556	(3,121)
Current	(77)	(92)	56
Deferred	945	1,648	(3,177)
Income tax expense (benefit)	868	1,556	(3,121)
United Airlines, Inc.
Income Taxes [Line Items]
Income tax provision at statutory rate	1,051	1,338	1,477
State income taxes, net of federal income tax	29	38	38
Foreign tax rate differential	(43)
Foreign income taxes	3	3	4
Nondeductible employee meals	17	16	15
Impact of Tax Act	(209)
Income tax adjustment from AOCI		180
State rate change	12	(12)
Valuation allowance	(16)	20	(4,621)
Other, net	8	(25)	7
Income tax expense (benefit)	852	1,558	(3,080)
Current	(77)	(92)	56
Deferred	929	1,650	(3,136)
Income tax expense (benefit)	$ 852	$ 1,558	$ (3,080)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Federal statutory income tax rate				35.00%		35.00%
Deferred income tax expense				$ 945	$ 1,648	$ (3,177)
Income tax benefit				192
Provisional one-time transition tax on previously deferred foreign earnings				19
Undistributed cumulative earnings of foreign subsidiaries contributing to one-time transition tax	$ 122			122
Income tax adjustments	(192)	$ 180		(192)	180	(3,130)
Valuation allowance	63	68		63	68
Unrecognized tax benefits	21	$ 74		21	74	24
Unrecognized tax benefits that would impact effective tax rate if recognized	21			$ 21
Scenario Forecast
Income Taxes [Line Items]
Federal statutory income tax rate			21.00%
Minimum
Income Taxes [Line Items]
State tax benefits of the NOL carry forwards expiration period, years				5 years
Maximum
Income Taxes [Line Items]
State tax benefits of the NOL carry forwards expiration period, years				20 years
2,026
Income Taxes [Line Items]
Net operating loss expiration amount	200			$ 200
2,029
Income Taxes [Line Items]
Net operating loss expiration amount	500			500
Thereafter
Income Taxes [Line Items]
Net operating loss expiration amount	1,700			1,700
Fuel | Designated as Hedging Instrument
Income Taxes [Line Items]
Deferred income tax expense					$ 180	$ 180
Federal
Income Taxes [Line Items]
NOL carry forwards	2,400			2,400
State
Income Taxes [Line Items]
NOL carry forwards	49			49
NOL carry forwards, net of valuation allowance	52			52
Valuation allowance	$ 63			$ 63

Components of Deferred Tax Asse

Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred income tax asset (liability):
Federal and state net operating loss ("NOL") carryforwards	$ 601	$ 1,613
Deferred revenue	1,069	2,096
Employee benefits, including pension, postretirement and medical	1,051	1,662
Alternative minimum tax credit carryforwards		116
Other	351	523
Less: Valuation allowance	(63)	(68)
Total deferred tax assets	3,009	5,942
Depreciation	(2,431)	(3,961)
Intangibles	(803)	(1,326)
Total deferred tax liabilities	(3,234)	(5,287)
Net deferred tax asset		655
Net deferred tax liabilities	(225)
United Airlines, Inc.
Deferred income tax asset (liability):
Federal and state net operating loss ("NOL") carryforwards	574	1,571
Deferred revenue	1,069	2,096
Employee benefits, including pension, postretirement and medical	1,051	1,662
Alternative minimum tax credit carryforwards		116
Other	351	522
Less: Valuation allowance	(63)	(68)
Total deferred tax assets	2,982	5,899
Depreciation	(2,431)	(3,961)
Intangibles	(803)	(1,326)
Total deferred tax liabilities	(3,234)	(5,287)
Net deferred tax asset		$ 612
Net deferred tax liabilities	$ (252)

Reconciliation of Change in Pro

Reconciliation of Change in Projected Benefit Obligation and Plan Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation:	$ 4,739	$ 4,158
Benefit obligation at beginning of year	5,253	4,473
Service cost	195	112	$ 124
Interest cost	220	200	200
Actuarial (gain) loss	525	738
Gross benefits paid and settlements	(366)	(243)
Other	25	(27)
Benefit obligation at end of year	5,852	5,253	4,473
Fair value of plan assets at beginning of year	3,355	2,975
Actual return on plan assets	510	230
Employer contributions	419	421
Gross benefits paid and settlements	(366)	(243)
Other	14	(28)
Fair value of plan assets at end of year	3,932	3,355	2,975
Funded status-Net amount recognized	(1,920)	(1,898)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at beginning of year	1,687	2,002
Service cost	13	19	21
Interest cost	66	86	82
Plan participants' contributions	68	69
Benefits paid	(178)	(191)
Actuarial (gain) loss	40	(165)
Plan amendments		(138)
Other	14	5
Benefit obligation at end of year	1,710	1,687	2,002
Fair value of plan assets at beginning of year	55	56
Actual return on plan assets	1	2
Employer contributions	108	119
Plan participants' contributions	68	69
Benefits paid	(178)	(191)
Fair value of plan assets at end of year	54	55	$ 56
Funded status-Net amount recognized	$ (1,656)	$ (1,632)

Amounts Recognized in Consolida

Amounts Recognized in Consolidated Balance Sheet and Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits
Amounts recognized in the consolidated balance sheets consist of:
Noncurrent asset	$ 9	$ 2
Current liability	(8)	(8)
Noncurrent liability	(1,921)	(1,892)
Total liability	(1,920)	(1,898)
Amounts recognized in accumulated other comprehensive income (loss) consist of:
Net actuarial gain (loss)	(1,610)	(1,482)
Prior service credit (loss)	(1)	(1)
Total accumulated other comprehensive income (loss)	(1,611)	(1,483)
Other Postretirement Benefits
Amounts recognized in the consolidated balance sheets consist of:
Current liability	(54)	(51)
Noncurrent liability	(1,602)	(1,581)
Total liability	(1,656)	(1,632)
Amounts recognized in accumulated other comprehensive income (loss) consist of:
Net actuarial gain (loss)	301	384
Prior service credit (loss)	208	245
Total accumulated other comprehensive income (loss)	$ 509	$ 629

Accumulated Benefit Obligation

Accumulated Benefit Obligation and Projected Benefit Obligation in Excess of Plan Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 5,637	$ 5,025
Accumulated benefit obligation	4,567	3,985
Fair value of plan assets	$ 3,709	$ 3,164

Components of Net Periodic Bene

Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 195	$ 112	$ 124
Interest cost	220	200	200
Expected return on plan assets	(243)	(216)	(194)
Amortization of unrecognized actuarial (gain) loss	128	76	85
Other	5	5	4
Net periodic benefit cost (credit)	305	177	219
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	13	19	21
Interest cost	66	86	82
Expected return on plan assets	(2)	(2)	(2)
Curtailment gain		(107)
Amortization of unrecognized actuarial (gain) loss	(33)	(19)	(22)
Amortization of prior service credits	(37)	(31)	(32)
Net periodic benefit cost (credit)	$ 7	$ (54)	$ 47

Amortized Accumulated Other Com

Amortized Accumulated Other Comprehensive Income (Loss) Into Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Actuarial (gain) loss	$ 132
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Actuarial (gain) loss		$ (32)
Prior service (credit) cost		$ (37)

Assumptions Used for Benefit Pl

Assumptions Used for Benefit Plans (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits
Assumptions used to determine benefit obligations
Discount rate	3.65%	4.18%
Rate of compensation increase	3.89%	3.54%
Assumptions used to determine net expense
Discount rate	4.19%	4.58%
Expected return on plan assets	7.02%	7.04%
Rate of compensation increase	3.54%	3.53%
Other Postretirement Benefits
Assumptions used to determine benefit obligations
Discount rate	3.63%	4.07%
Assumptions used to determine net expense
Discount rate	4.07%	4.49%
Expected return on plan assets	3.00%	3.00%
Health care cost trend rate assumed for next year	6.25%	6.50%
Rate to which the cost trend rate is assumed to decline (ultimate trend rate in 2023)	5.00%	5.00%

Allocation of Plan Assets (Deta

Allocation of Plan Assets (Detail) - United Airlines, Inc.	12 Months Ended
	Dec. 31, 2017
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Expected Long-Term Rate of Return	9.50%
Equity Securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Percent of Total	27.00%
Equity Securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Percent of Total	42.00%
Fixed-Income Securities
Defined Benefit Plan Disclosure [Line Items]
Expected Long-Term Rate of Return	5.50%
Fixed-Income Securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Percent of Total	30.00%
Fixed-Income Securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Percent of Total	40.00%
Alternatives
Defined Benefit Plan Disclosure [Line Items]
Expected Long-Term Rate of Return	7.30%
Alternatives | Minimum
Defined Benefit Plan Disclosure [Line Items]
Percent of Total	10.00%
Alternatives | Maximum
Defined Benefit Plan Disclosure [Line Items]
Percent of Total	25.00%
Other Investments
Defined Benefit Plan Disclosure [Line Items]
Expected Long-Term Rate of Return	7.30%
Other Investments | Minimum
Defined Benefit Plan Disclosure [Line Items]
Percent of Total	0.00%
Other Investments | Maximum
Defined Benefit Plan Disclosure [Line Items]
Percent of Total	10.00%

Pension and Other Postretirem68

Pension and Other Postretirement Plans (Defined Pension and Other Postretirement Plans) - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Effect on post retirement benefit obligation, 1% Decrease		$ 185
Effect on benefit expense, 1% Decrease		8
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Employer contributions		$ 108	$ 119
Other Postretirement Benefits | Deposit Administration Fund
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets		100.00%
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Employer contributions		$ 419	$ 421
United Airlines, Inc. | Other Postretirement Benefits | Scenario Forecast
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 109
United Airlines, Inc. | Pension Benefits | Scenario Forecast
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 420

Effect of One-Percentage-Point

Effect of One-Percentage-Point Change in Assumed Health Care Trend Rate (Detail) - Other Postretirement Benefits $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Defined Benefit Plan Disclosure [Line Items]
Effect on total service and interest cost, 1% Increase	$ 11
Effect on post retirement benefit obligation, 1% Increase	170
Effect on total service and interest cost,1% Decrease	(8)
Effect on post retirement benefit obligation, 1% Decrease	$ (149)

Pension and Other Postretirem70

Pension and Other Postretirement Plan Assets (Detail) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		$ 3,932	$ 3,355	$ 2,975
Assets measured at NAV	[1]	2,211	1,843
Pension Benefits | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		1,406	1,173
Assets measured at NAV	[1]	1,004	832
Pension Benefits | Fixed-Income Securities
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		1,470	1,298
Assets measured at NAV	[1]	618	463
Pension Benefits | Alternatives
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		637	586
Assets measured at NAV	[1]	498	452
Pension Benefits | Other Investments
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		419	298
Assets measured at NAV	[1]	91	96
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		54	55	56
Other Postretirement Benefits | Deposit Administration Fund
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		54	55
Level 1 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		301	277
Level 1 | Pension Benefits | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		269	230
Level 1 | Pension Benefits | Other Investments
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		32	47
Level 2 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		1,091	1,003
Level 2 | Pension Benefits | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		133	111
Level 2 | Pension Benefits | Fixed-Income Securities
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		834	824
Level 2 | Pension Benefits | Other Investments
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		124	68
Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		383	287	$ 208
Level 3 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		329	232
Level 3 | Pension Benefits | Fixed-Income Securities
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		18	11
Level 3 | Pension Benefits | Alternatives
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		139	134
Level 3 | Pension Benefits | Other Investments
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		172	87
Level 3 | Other Postretirement Benefits | Deposit Administration Fund
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement plan assets		$ 54	$ 55
[1]	In accordance with the relevant accounting standards, certain investments that are measured at fair value using the net asset value ("NAV") per share (or its equivalent) have not been classified in the fair value hierarchy. These investments are commingled funds that invest in fixed-income instruments including bonds, debt securities, and other similar instruments issued by various U.S. and non-U.S. public- or private-sector entities. Redemption periods for these investments range from daily to annually.

Defined Benefit Plan Assets Mea

Defined Benefit Plan Assets Measured at Fair Value Using Unobservable Inputs (Level Three) (Detail) - Level 3 - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	$ 287	$ 208
Actual return on plan assets, Sold during the year	7	4
Actual return on plan assets, Held at year end	16	3
Purchases, sales, issuances and settlements (net)	73	72
Fair value of plan assets at end of year	$ 383	$ 287

Estimated Future Benefit Paymen

Estimated Future Benefit Payments (Detail) $ in Millions	Dec. 31, 2017USD ($)
Defined Benefit Plan Disclosure [Line Items]
2,018	$ 6
2,019	6
2,020	6
2,021	7
2,022	7
Years 2023 - 2027	43
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
2,018	305
2,019	326
2,020	331
2,021	357
2,022	369
Years 2023 - 2027	1,912
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
2,018	113
2,019	118
2,020	121
2,021	124
2,022	126
Years 2023 - 2027	$ 646

Pension and Other Postretirem73

Pension and Other Postretirement Plans (Defined Contribution Plans) - Additional Information (Detail) - United Airlines, Inc. - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, employer	$ 656	$ 592	$ 522
Minimum
Defined Contribution Plan Disclosure [Line Items]
Employer contribution, percentage	1.00%
Maximum
Defined Contribution Plan Disclosure [Line Items]
Employer contribution, percentage	16.00%

Pension and Other Postretirem74

Pension and Other Postretirement Plans (Multi-Employer Plans) - Additional Information (Detail) - Multiemployer Plans, Pension - IAM National Pension Plan $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)
Multiemployer Plans [Line Items]
Multi-employer plan contributions	$ 414
Minimum
Multiemployer Plans [Line Items]
Percent of company's contribution to plan	5.00%

Multi-Employer Plans (Detail)

Multi-Employer Plans (Detail) - Multiemployer Plans, Pension - IAM National Pension Plan - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Multiemployer Plans [Line Items]
EIN		516,031,295
Pension Plan Number		2
Pension Protection Act Zone Status (2016 and 2015)	[1]	Green
FIP/RP Status Pending/Implemented		No
Surcharge Imposed		No
United Airlines, Inc.
Multiemployer Plans [Line Items]
United's Contributions		$ 50	$ 41	$ 40
[1]	At the date the Consolidated Financial Statements were issued, Forms 5500 were not available for the plan year ending in 2017.

Pension and Other Postretirem76

Pension and Other Postretirement Plans (Profit Sharing) - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Profit sharing and payroll tax expense	$ 349	$ 628	$ 698
Minimum
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Percentage of pre-tax earnings paid for profit sharing plan	5.00%
Maximum
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Percentage of pre-tax earnings paid for profit sharing plan	20.00%

Financial Assets and Liabilitie

Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 1,482	$ 2,179
Restricted cash	109	124
Equity securities	99
Enhanced equipment trust certificates ("EETC")	22	23
Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	958	835
Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	753	792
CDARS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	120	246
U.S. Government and Agency Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	113	140
Other Fixed Income Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	188	54
Other Investments Measured At NAV
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	184	182
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	1,482	2,179
Restricted cash	109	124
Equity securities	99
Level 2 | Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	958	835
Level 2 | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	753	792
Level 2 | CDARS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	120	246
Level 2 | U.S. Government and Agency Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	113	140
Level 2 | Other Fixed Income Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	188	54
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Enhanced equipment trust certificates ("EETC")	$ 22	$ 23

Fair Value Measurements and I78

Fair Value Measurements and Investments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017
EETC
Fair Value [Line Items]
Available-for-sale securities remaining maturities	2,019
Asset-backed Securities | Minimum
Fair Value [Line Items]
Available-for-sale securities remaining maturities	1 year
Asset-backed Securities | Maximum
Fair Value [Line Items]
Available-for-sale securities remaining maturities	17 years
Corporate Debt | Minimum
Fair Value [Line Items]
Available-for-sale securities remaining maturities	1 year
Corporate Debt | Maximum
Fair Value [Line Items]
Available-for-sale securities remaining maturities	3 years
CDARS | Maximum
Fair Value [Line Items]
Available-for-sale securities remaining maturities	1 year
U.S. Government and Other Securities | Minimum
Fair Value [Line Items]
Available-for-sale securities remaining maturities	1 year
U.S. Government and Other Securities | Maximum
Fair Value [Line Items]
Available-for-sale securities remaining maturities	3 years

Carrying Values and Estimated F

Carrying Values and Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Carrying (Reported) Amount, Fair Value Disclosure
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 13,268	$ 10,767
Estimate of Fair Value, Fair Value Disclosure
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt fair value	13,787	11,055
Estimate of Fair Value, Fair Value Disclosure | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt fair value
Estimate of Fair Value, Fair Value Disclosure | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt fair value	10,115	8,184
Estimate of Fair Value, Fair Value Disclosure | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt fair value	$ 3,672	$ 2,871

Debt (Detail)

Debt (Detail) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Less: current portion of long-term debt		$ (1,565)	$ (849)
Long-term debt, net		11,703	9,918
United Airlines, Inc.
Debt Instrument [Line Items]
Less: current portion of long-term debt		(1,565)	(849)
Long-term debt, net		11,703	9,918
UAL and United
Debt Instrument [Line Items]
Long-term Debt, Gross		13,431	10,891
Less: unamortized debt discount, premiums and debt issuance costs		(163)	(124)
Less: current portion of long-term debt		(1,565)	(849)
Long-term debt, net		11,703	9,918
Secured Debt | Notes payable, fixed interest rates of 2.88% to 9.52% (weighted average rate of 4.39% as of December 31, 2017), payable through 2028 | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross		8,661	7,586
Secured Debt | Notes payable, floating interest rates of the London interbank offered rate ("LIBOR") plus 0.2% to 2.25%, payable through 2028 | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross		1,880	1,546
Secured Debt | Term Loan Facility Due 2024 | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross		1,489
Secured Debt | Term Loan Facility Due April 2019 | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross			866
Secured Debt | Term Loan Facility Due September 2021 | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross			192
Unsecured Debt | 6.375% Senior Notes due 2018
Debt Instrument [Line Items]
Long-term Debt, Gross	[1]	300	300
Unsecured Debt | 6% Senior Notes due 2020
Debt Instrument [Line Items]
Long-term Debt, Gross	[1]	300	300
Unsecured Debt | 4.25% Senior Notes due 2022 | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross	[1]	400
Unsecured Debt | 5% Senior Notes due 2024 | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross	[1]	300
Unsecured Debt | Other Debt | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 101	$ 101
[1]	UAL is the issuer of this debt. United is a guarantor.

Debt (Parenthetical) (Detail)

Debt (Parenthetical) (Detail)		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017	Jan. 30, 2017
Notes payable, fixed interest rates of 2.88% to 9.52% (weighted average rate of 4.39% as of December 31, 2017), payable through 2028 | United Airlines, Inc. | Secured Debt
Debt Instrument [Line Items]
Weighted average interest rate		4.39%
Debt instrument, maturity date		2,028	2,028
Notes payable, fixed interest rates of 2.88% to 9.52% (weighted average rate of 4.39% as of December 31, 2017), payable through 2028 | United Airlines, Inc. | Secured Debt | Minimum
Debt Instrument [Line Items]
Debt instrument stated interest rate		2.88%
Notes payable, fixed interest rates of 2.88% to 9.52% (weighted average rate of 4.39% as of December 31, 2017), payable through 2028 | United Airlines, Inc. | Secured Debt | Maximum
Debt Instrument [Line Items]
Debt instrument stated interest rate		9.52%
Notes payable, floating interest rates of the London interbank offered rate ("LIBOR") plus 0.2% to 2.25%, payable through 2028 | United Airlines, Inc. | Secured Debt
Debt Instrument [Line Items]
Debt instrument, maturity date		2,028	2,028
Notes payable, floating interest rates of the London interbank offered rate ("LIBOR") plus 0.2% to 2.25%, payable through 2028 | United Airlines, Inc. | Secured Debt | LIBOR | Minimum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		0.20%
Notes payable, floating interest rates of the London interbank offered rate ("LIBOR") plus 0.2% to 2.25%, payable through 2028 | United Airlines, Inc. | Secured Debt | LIBOR | Maximum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		2.25%
Term Loan Facility Due 2024 | United Airlines, Inc. | Secured Debt
Debt Instrument [Line Items]
Debt instrument, maturity date		2,024
Term Loan Facility Due 2024 | United Airlines, Inc. | Secured Debt | LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		2.00%
Term Loan Facility Due 2024 | United Airlines, Inc. | Secured Debt | Certain Market Interest Rates
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.00%
Term Loan Facility Due April 2019 | United Airlines, Inc. | Secured Debt
Debt Instrument [Line Items]
Debt instrument, maturity date		2,019	2,019
Term Loan Facility Due April 2019 | United Airlines, Inc. | Secured Debt | LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		2.50%	2.50%
Term Loan Facility Due April 2019 | United Airlines, Inc. | Secured Debt | Certain Market Interest Rates
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.50%	1.50%
Term Loan Facility Due April 2019 | United Airlines, Inc. | Secured Debt | Interest Rate Floor
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		0.75%	0.75%
Term Loan Facility Due September 2021 | United Airlines, Inc. | Secured Debt
Debt Instrument [Line Items]
Debt instrument, maturity date		2,021	2,021
Term Loan Facility Due September 2021 | United Airlines, Inc. | Secured Debt | LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		2.75%	2.75%
Term Loan Facility Due September 2021 | United Airlines, Inc. | Secured Debt | Certain Market Interest Rates
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.75%	1.75%
Term Loan Facility Due September 2021 | United Airlines, Inc. | Secured Debt | Interest Rate Floor
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		0.75%	0.75%
6.375% Senior Notes due 2018
Debt Instrument [Line Items]
Debt instrument stated interest rate		6.375%
6.375% Senior Notes due 2018 | Unsecured Debt
Debt Instrument [Line Items]
Debt instrument stated interest rate	[1]	6.375%	6.375%
Debt instrument, maturity date	[1]	2,018	2,018
6% Senior Notes due 2020
Debt Instrument [Line Items]
Debt instrument stated interest rate		6.00%
6% Senior Notes due 2020 | Unsecured Debt
Debt Instrument [Line Items]
Debt instrument stated interest rate	[1]	6.00%	6.00%
Debt instrument, maturity date	[1]	2,020	2,020
4.25% Senior Notes due 2022
Debt Instrument [Line Items]
Debt instrument stated interest rate		4.25%
4.25% Senior Notes due 2022 | United Airlines, Inc.
Debt Instrument [Line Items]
Debt instrument stated interest rate				4.25%
4.25% Senior Notes due 2022 | United Airlines, Inc. | Unsecured Debt
Debt Instrument [Line Items]
Debt instrument stated interest rate	[1]	4.25%	4.25%
Debt instrument, maturity date	[1]	2,022	2,022
5% Senior Notes due 2024
Debt Instrument [Line Items]
Debt instrument stated interest rate		5.00%
5% Senior Notes due 2024 | United Airlines, Inc.
Debt Instrument [Line Items]
Debt instrument stated interest rate					5.00%
5% Senior Notes due 2024 | United Airlines, Inc. | Unsecured Debt
Debt Instrument [Line Items]
Debt instrument stated interest rate	[1]	5.00%	5.00%
Debt instrument, maturity date	[1]	2,024	2,024
[1]	UAL is the issuer of this debt. United is a guarantor.

Contractual Principal Payments

Contractual Principal Payments (Detail) - UAL and United - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
2,018	$ 1,565
2,019	1,165
2,020	1,170
2,021	1,157
2,022	1,492
After 2,022	6,882
Long-term debt	$ 13,431	$ 10,891

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)	1 Months Ended		12 Months Ended
	Sep. 30, 2017	Jan. 30, 2017	Dec. 31, 2017	Nov. 30, 2017
4.25% Senior Notes due 2022
Debt Instrument [Line Items]
Debt instrument stated interest rate			4.25%
5% Senior Notes due 2024
Debt Instrument [Line Items]
Debt instrument stated interest rate			5.00%
United Airlines, Inc.
Debt Instrument [Line Items]
Aggregate principal amount			$ 497,000,000
United Airlines, Inc. | Pass-through certificates
Debt Instrument [Line Items]
Long term debt			8,600,000,000
United Airlines, Inc. | 4.25% Senior Notes due 2022
Debt Instrument [Line Items]
Aggregate principal amount	$ 400,000,000
Debt instrument maturity date	Oct. 1, 2022
Debt instrument stated interest rate	4.25%
Notes repurchase price	101.00%
United Airlines, Inc. | 5% Senior Notes due 2024
Debt Instrument [Line Items]
Aggregate principal amount		$ 300,000,000
Debt instrument maturity date		Feb. 1, 2024
Debt instrument stated interest rate		5.00%
Notes repurchase price		101.00%
United Airlines, Inc. | Surety Bond
Debt Instrument [Line Items]
Credit facility outstanding amount			$ 362,000,000
Credit facility expiration year			2,021
United Airlines, Inc. | Revolving Credit Facility
Debt Instrument [Line Items]
Commitment fee percentage			0.75%
United Airlines, Inc. | Letters of credit | Cash Collateralized Letters of Credit
Debt Instrument [Line Items]
Credit facility outstanding amount			$ 75,000,000
United Airlines, Inc. | Secured Debt
Debt Instrument [Line Items]
Quarterly principal repayment amount			0.25%
United Airlines, Inc. | Secured Debt | Term Loan Due April 1, 2024 [Member] | LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate			2.00%
United Airlines, Inc. | Secured Debt | Term Loan Due April 1, 2024 [Member] | Certain Market Interest Rates
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate			1.00%
United Airlines, Inc. | Secured Debt | Term Loan Facility Due April 1, 2024
Debt Instrument [Line Items]
Aggregate principal amount			$ 1,500,000,000
Debt instrument maturity date			Apr. 1, 2024
Increase in term loan balance			$ 440,000,000
Interest on borrowings reduction percentage				0.25%
United Airlines, Inc. | Secured Debt | Revolving Credit Facility
Debt Instrument [Line Items]
Available under revolving credit facility			2,000,000,000
United Airlines, Inc. | Secured Debt | Revolving Credit Facility Available For Drawing Until April 1, 2022
Debt Instrument [Line Items]
Credit agreement			$ 2,000,000,000
Revolving credit facility available for drawing date			Apr. 1, 2022

Details of Pass Through Trusts

Details of Pass Through Trusts (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Proceeds received from issuance of debt	$ 2,765	$ 808	$ 1,073
United Airlines, Inc.
Debt Instrument [Line Items]
Principal	497
Proceeds received from issuance of debt	2,765	$ 808	$ 1,073
United Airlines, Inc. | Class B Pass Through Certificates | November 2017
Debt Instrument [Line Items]
Principal	$ 258
Final expected distribution date	2026-01
Stated interest rate	3.65%
Total debt recorded	$ 258
Proceeds received from issuance of debt	258
United Airlines, Inc. | Class B Pass Through Certificates One | November 2017
Debt Instrument [Line Items]
Principal	$ 236
Final expected distribution date	2025-10
Stated interest rate	3.65%
Total debt recorded	$ 236
Proceeds received from issuance of debt	236
United Airlines, Inc. | Class AA Pass Through Certificates | February Twenty Eighteen [Member]
Debt Instrument [Line Items]
Principal	$ 677
Final expected distribution date	2030-03
Stated interest rate	3.50%
Remaining proceeds from issuance of debt to be received in future periods	$ 677
United Airlines, Inc. | Class AA Pass Through Certificates | September 2016
Debt Instrument [Line Items]
Principal	$ 637
Final expected distribution date	2028-10
Stated interest rate	2.875%
Total debt recorded	$ 637
Proceeds received from issuance of debt	557
United Airlines, Inc. | Class AA Pass Through Certificates | June 2016
Debt Instrument [Line Items]
Principal	$ 729
Final expected distribution date	2028-07
Stated interest rate	3.10%
Total debt recorded	$ 729
Proceeds received from issuance of debt	319
United Airlines, Inc. | Class A Pass Through Certificates | February Twenty Eighteen [Member]
Debt Instrument [Line Items]
Principal	$ 258
Final expected distribution date	2030-03
Stated interest rate	3.70%
Remaining proceeds from issuance of debt to be received in future periods	$ 258
United Airlines, Inc. | Class A Pass Through Certificates | September 2016
Debt Instrument [Line Items]
Principal	$ 283
Final expected distribution date	2028-10
Stated interest rate	3.10%
Total debt recorded	$ 283
Proceeds received from issuance of debt	247
United Airlines, Inc. | Class A Pass Through Certificates | June 2016
Debt Instrument [Line Items]
Principal	$ 324
Final expected distribution date	2028-07
Stated interest rate	3.45%
Total debt recorded	$ 324
Proceeds received from issuance of debt	142
United Airlines, Inc. | EETC
Debt Instrument [Line Items]
Principal	3,402
Total debt recorded	2,467
Proceeds received from issuance of debt	1,759
Remaining proceeds from issuance of debt to be received in future periods	$ 935

Summary of Collateral Covenants

Summary of Collateral Covenants and Cross Default Provisions (Detail)	12 Months Ended
	Dec. 31, 2017
Credit Agreement
Debt Instrument [Line Items]
Collateral, Covenants and Cross Default Provisions	Secured by certain of United’s international route authorities, specified take-off and landing slots at certain airports and certain other assets. The 2017 Credit Agreement requires the Company to maintain at least $2.0 billion of unrestricted liquidity at all times, which includes unrestricted cash, short-term investments and any undrawn amounts under any revolving credit facility, and to maintain a minimum ratio of appraised value of collateral to the outstanding obligations under the 2017 Credit Agreement of 1.6 to 1.0 at all times. The 2017 Credit Agreement contains covenants that, among other things, restrict the ability of UAL and its restricted subsidiaries (as defined in the 2017 Credit Agreement) to incur additional indebtedness and to pay dividends on or repurchase stock, although the Company currently has ample ability under these restrictions to repurchase stock under the Company’s share repurchase program. The 2017 Credit Agreement contains events of default customary for this type of financing, including a cross default and cross acceleration provision to certain other material indebtedness of the Company.
6.375% Senior Notes due 2018
Debt Instrument [Line Items]
Collateral, Covenants and Cross Default Provisions	The indentures for these notes contain covenants that, among other things, restrict the ability of the Company and its restricted subsidiaries (as defined in the indentures) to incur additional indebtedness and pay dividends on or repurchase stock, although the Company currently has ample ability under these restrictions to repurchase stock under the Company’s share repurchase program.
6% Senior Notes due 2020
Debt Instrument [Line Items]
Collateral, Covenants and Cross Default Provisions	The indentures for these notes contain covenants that, among other things, restrict the ability of the Company and its restricted subsidiaries (as defined in the indentures) to incur additional indebtedness and pay dividends on or repurchase stock, although the Company currently has ample ability under these restrictions to repurchase stock under the Company’s share repurchase program.
5% Senior Notes due 2024
Debt Instrument [Line Items]
Collateral, Covenants and Cross Default Provisions	The indentures for these notes contain covenants that, among other things, restrict the ability of the Company and its restricted subsidiaries (as defined in the indentures) to incur additional indebtedness and pay dividends on or repurchase stock, although the Company currently has ample ability under these restrictions to repurchase stock under the Company’s share repurchase program.
4.25% Senior Notes due 2022
Debt Instrument [Line Items]
Collateral, Covenants and Cross Default Provisions	The indentures for these notes contain covenants that, among other things, restrict the ability of the Company and its restricted subsidiaries (as defined in the indentures) to incur additional indebtedness and pay dividends on or repurchase stock, although the Company currently has ample ability under these restrictions to repurchase stock under the Company’s share repurchase program.

Summary of Collateral Covenan86

Summary of Collateral Covenants and Cross Default Provisions (Parenthetical) (Detail) $ in Billions	12 Months Ended
	Dec. 31, 2017USD ($)
Credit Agreement
Debt Instrument [Line Items]
Unrestricted liquidity required for credit agreement	$ 2
Minimum ratio of appraised value of collateral for Credit Agreement	160.00%
6.375% Senior Notes due 2018
Debt Instrument [Line Items]
Debt instrument stated interest rate	6.375%
Debt instrument maturity year	2,018
6% Senior Notes due 2020
Debt Instrument [Line Items]
Debt instrument stated interest rate	6.00%
Debt instrument maturity year	2,020
5% Senior Notes due 2024
Debt Instrument [Line Items]
Debt instrument stated interest rate	5.00%
Debt instrument maturity year	2,024
4.25% Senior Notes due 2022
Debt Instrument [Line Items]
Debt instrument stated interest rate	4.25%
Debt instrument maturity year	2,022

Future Minimum Lease Payments f

Future Minimum Lease Payments for Capital and Operating Leases (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Capital Leases
2,018	$ 200
2,019	133
2,020	113
2,021	110
2,022	105
After 2,022	1,156
Minimum lease payments	1,817
Imputed interest	(693)
Present value of minimum lease payments	1,124
Current portion	(128)	$ (116)
Long-term obligations under capital leases	996	$ 822
Present value of minimum lease payments	1,124
Facility and Other Operating Leases
Operating Leases
2,018	1,234
2,019	1,075
2,020	1,169
2,021	935
2,022	797
After 2,022	6,109
Minimum lease payments	11,319
Aircraft Operating Leases
Operating Leases
2,018	1,038
2,019	855
2,020	628
2,021	510
2,022	388
After 2,022	1,513
Minimum lease payments	$ 4,932

Future Minimum Lease Payments88

Future Minimum Lease Payments for Capital and Operating Leases (Parenthetical) (Detail) - Airport Construction Projects [Member] $ in Millions	Dec. 31, 2017USD ($)
Capital Leases And Operating Leases [Line Items]
Other operating property and equipment	$ 814
Current and long-term obligations under capital leases	$ 777

Leases and Capacity Purchase 89

Leases and Capacity Purchase Agreements - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)Aircraft	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Capital Leased Assets [Line Items]
Regional capacity purchase expense		$ 2,232,000,000	$ 2,197,000,000	$ 2,290,000,000
Expenses		34,238,000,000	32,218,000,000	32,698,000,000
Accounts payable		2,196,000,000	2,139,000,000
Capacity Purchase Agreements | Scenario Forecast
Capital Leased Assets [Line Items]
Scheduled block hours increase (decrease) percentage	10.00%
Change in cash obligation	$ 147,000,000
Aircraft Operating Leases
Capital Leased Assets [Line Items]
Operating leases obligations		$ 4,932,000,000
Minimum | Aircraft Operating Leases
Capital Leased Assets [Line Items]
Operating lease term		5 years
Operating lease expiration date, in years		2,018
Maximum | Aircraft Operating Leases
Capital Leased Assets [Line Items]
Operating lease term		26 years
Operating lease expiration date, in years		2,029
United Airlines, Inc.
Capital Leased Assets [Line Items]
Nonaircraft rent expense		$ 1,300,000,000	1,200,000,000	1,300,000,000
Regional capacity purchase expense		$ 2,232,000,000	2,197,000,000	2,290,000,000
Number of aircrafts under the extended term of contract | Aircraft		125
Capacity purchase agreement contract expiration date after extension		Dec. 31, 2022
Expenses		$ 34,236,000,000	32,215,000,000	32,696,000,000
Accounts payable		$ 2,196,000,000	2,144,000,000
United Airlines, Inc. | Capacity Purchase Agreements
Capital Leased Assets [Line Items]
Number of regional aircraft | Aircraft		518
Airline capacity purchase arrangements, expiration year		2,029
United Airlines, Inc. | Revaluation of Liabilities
Capital Leased Assets [Line Items]
Net accretion amounts		$ 79,000,000	82,000,000	107,000,000
United Airlines, Inc. | Regional Aircraft
Capital Leased Assets [Line Items]
Regional capacity purchase expense		458,000,000	439,000,000	461,000,000
United Airlines, Inc. | Variable Interest Entity, Not Primary Beneficiary
Capital Leased Assets [Line Items]
Operating leases obligations		$ 1,400,000,000
United Airlines, Inc. | Minimum
Capital Leased Assets [Line Items]
Imputed interest rate		3.50%
Lease Fair Value Adjustment, Remaining Lease Term		1 year
United Airlines, Inc. | Maximum
Capital Leased Assets [Line Items]
Imputed interest rate		20.80%
Lease Fair Value Adjustment, Remaining Lease Term		7 years
United Airlines, Inc. | Maximum | CRJ 200
Capital Leased Assets [Line Items]
Number of aircraft to operate | Aircraft		65
United Airlines, Inc. | Mainline
Capital Leased Assets [Line Items]
Number of assets subject to lease | Aircraft		31
United Airlines, Inc. | Regional Carrier
Capital Leased Assets [Line Items]
Number of assets subject to lease | Aircraft		43
United Airlines, Inc. | Regional Carrier | Capacity Purchase Agreements
Capital Leased Assets [Line Items]
Expenses		$ 538,000,000	486,000,000	$ 366,000,000
Accounts payable		24,000,000	32,000,000
Accounts receivable from regional carriers		$ 0	$ 0

Future Lease Payment Under Term

Future Lease Payment Under Terms of Capacity Purchase Agreement (Detail) $ in Billions	Dec. 31, 2017USD ($)
Long-term Purchase Commitment [Line Items]
2,018	$ 2
2,019	1.8
2,020	1.6
2,021	1.5
2,022	1.4
After 2,022	3.2
Contractual Obligation, Total	$ 11.5

Variable Interest Entities - Ad

Variable Interest Entities - Additional Information (Detail) - Variable Interest Entity, Not Primary Beneficiary	Dec. 31, 2017Aircraft
Mainline
Variable Interest Entity [Line Items]
Aircraft under operating lease, fixed purchase options	38
Regional Carrier
Variable Interest Entity [Line Items]
Aircraft under operating lease	158

Schedule of Commitments to Purc

Schedule of Commitments to Purchase Aircrafts (Detail) - United Airlines, Inc. - Capital Addition Purchase Commitments	Dec. 31, 2017Aircraft	[1]
Airbus A350 Aircraft
Long-term Purchase Commitment [Line Items]
Number of new aircraft committed to purchase	45
Boeing 737 MAX Aircraft
Long-term Purchase Commitment [Line Items]
Number of new aircraft committed to purchase	161
Boeing 777-300ER Aircraft
Long-term Purchase Commitment [Line Items]
Number of new aircraft committed to purchase	4
Boeing 787 Aircraft
Long-term Purchase Commitment [Line Items]
Number of new aircraft committed to purchase	18
[1]	United also has options and purchase rights for additional aircraft.

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)EmployeeOptionAircraft	Feb. 28, 2018USD ($)
Commitments and Contingencies [Line Items]
Aggregate balance	$ 11,500,000,000
Number of call options to purchase regional jet aircraft | Option	257
Subsequent Event | EETC
Commitments and Contingencies [Line Items]
Debt instrument principal amount		$ 935,000,000
Boeing 737 MAX Aircraft [Member]
Commitments and Contingencies [Line Items]
Number of aircrafts expects to take delivery | Aircraft	10
Boeing 787 Aircraft [Member]
Commitments and Contingencies [Line Items]
Number of aircrafts expects to take delivery | Aircraft	7
Boeing 777-300ER Aircraft [Member]
Commitments and Contingencies [Line Items]
Number of aircrafts expects to take delivery | Aircraft	4
Aircraft Mortgage Debt
Commitments and Contingencies [Line Items]
Guarantor obligations, maximum exposure	$ 157,000,000
Tax-exempt special facilities revenue bonds
Commitments and Contingencies [Line Items]
Guarantor obligations, maximum exposure	1,800,000,000
Operating leases obligations	1,400,000,000
Capital leases obligations	441,000,000
Tax-exempt special facilities revenue bonds | Indirect Guarantee of Indebtedness
Commitments and Contingencies [Line Items]
Guarantor obligations, maximum exposure	244,000,000
Contingent liabilities based on participation	1,500,000,000
Floating Rate Debt
Commitments and Contingencies [Line Items]
Debt instrument principal amount	3,400,000,000
Fixed Rate Debt
Commitments and Contingencies [Line Items]
Debt instrument principal amount	60,000,000
Loans And Leases From Non U S Entities
Commitments and Contingencies [Line Items]
Aggregate balance	$ 3,300,000,000
Minimum | Tax-exempt special facilities revenue bonds
Commitments and Contingencies [Line Items]
Debt instrument maturity year	2,019
Minimum | Tax-exempt special facilities revenue bonds | Indirect Guarantee of Indebtedness
Commitments and Contingencies [Line Items]
Debt instrument maturity year	2,022
Maximum
Commitments and Contingencies [Line Items]
Debt instrument, remaining terms (years)	11 years
Maximum | Tax-exempt special facilities revenue bonds
Commitments and Contingencies [Line Items]
Debt instrument maturity year	2,038
Maximum | Tax-exempt special facilities revenue bonds | Indirect Guarantee of Indebtedness
Commitments and Contingencies [Line Items]
Debt instrument maturity year	2,049
Maximum | Loans And Leases From Non U S Entities
Commitments and Contingencies [Line Items]
Debt instrument, remaining terms (years)	11 years
United Airlines, Inc.
Commitments and Contingencies [Line Items]
Debt instrument principal amount	$ 497,000,000
Number of employees | Employee	89,800
Percentage of employees represented by various U.S. labor organizations	80.00%
United Airlines, Inc. | EETC
Commitments and Contingencies [Line Items]
Debt instrument principal amount	$ 3,402,000,000

Schedule of Acquisition of Airc

Schedule of Acquisition of Aircrafts and Related Spare Engines (Detail) $ in Billions	Dec. 31, 2017USD ($)
Unrecorded Unconditional Purchase Obligation [Line Items]
2,018	$ 3.2
2,019	2.9
2,020	2.1
2,021	2.4
2,022	1.8
After 2,022	9.8
Total commitments	$ 22.2

Components of Special Charges (

Components of Special Charges (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating:
Severance and benefit costs	$ 15	$ 23	$ 41	$ 37	$ 10	$ 13	$ 6	$ 8	$ 116	$ 37	$ 107
Impairment of assets	10	15					412		25	412	79
Cleveland airport lease restructuring								74		74
Labor agreement costs					(60)	14	10	100		64	18
(Gains) losses on sale of assets and other special charges	6	12	3	14	19	18	6	8	35	51	122
Total operating special charges	31	50	44	51	(31)	45	434	190	176	638	326
Nonoperating income (expense):
(Gains) losses on extinguishment of debt and other							(9)	8		(1)	202
Total operating and nonoperating special charges before income taxes									176	637	528
Income tax benefit related to special charges	(11)	(18)	(16)	(18)	12	(16)	(153)	(72)	(63)	(229)	(11)
Income tax adjustments (Notes 6 and 7)	(192)				180				(192)	180	(3,130)
Total operating and nonoperating special charges, net of income taxes and income tax adjustments	$ (172)	$ 32	$ 28	$ 33	$ 161	$ 29	$ 272	$ 126	$ (79)	$ 588	$ (2,613)

Special Charges - Additional In

Special Charges - Additional Information (Detail)	3 Months Ended									12 Months Ended
	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)Technician	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)VEF / $	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)Contractplan	Dec. 31, 2015USD ($)VEF / $	Dec. 31, 2014USD ($)Attendant
Special Charges [Line Items]
Severance and benefits costs	$ 15,000,000	$ 23,000,000	$ 41,000,000	$ 37,000,000	$ 10,000,000	$ 13,000,000	$ 6,000,000	$ 8,000,000		$ 116,000,000	$ 37,000,000	$ 107,000,000
Severance and benefits costs net of tax											24,000,000
Impairment of assets	$ 10,000,000	$ 15,000,000					412,000,000			25,000,000	$ 412,000,000	79,000,000
Impairment of indefinite-lived intangible assets									$ 33,000,000
Impairment of indefinite-lived intangible assets, net of tax benefits									22,000,000
Lease maturity year											2,029
Cleveland airport lease restructuring								74,000,000			$ 74,000,000
Cleveland airport lease restructuring, net of taxes											47,000,000
Labor agreement costs					$ (60,000,000)	$ 14,000,000	10,000,000	100,000,000			64,000,000	18,000,000
Costs associated with aircraft									8,000,000
Inventory held for sale									$ 7,000,000			7,000,000
Impairment for discontinued internal software projects												10,000,000
Impairment of assets held for disposal												10,000,000
Collective bargaining agreements												18,000,000
Integration-related costs												60,000,000
Charges for legal matters												32,000,000
Cease use of an aircraft under lease												16,000,000
Losses (gain) on extinguishment of debt and other							$ (9,000,000)	$ 8,000,000			$ (1,000,000)	202,000,000
Venezuela local currency loss												$ 61,000,000
Foreign currency exchange rate | VEF / $									200			200
Foreign currency exchange rate per US dollar, description												200 Venezuelan bolivars to one U.S. dollar
Venezuelan bolivars
Special Charges [Line Items]
Unrestricted cash balance held as Venezuelan bolivars									$ 13,000,000			$ 13,000,000
Postretirement Medical Plan | Flight Attendant Postretirement Medical Plan
Special Charges [Line Items]
Number of plans amended | plan											2
Curtailment gain recognition of prior service credit											$ 47,000,000
Curtailment gain recognition of prior service credit,net of tax											30,000,000
Newark Liberty International Airport
Special Charges [Line Items]
Impairment of indefinite-lived intangible assets											412,000,000
Impairment of indefinite-lived intangible assets, net of tax benefits											264,000,000
United Airlines, Inc. | 6% Notes due 2026 and 2028
Special Charges [Line Items]
Write off of unamortized discount												$ 134,000,000
Scenario, Previously Reported
Special Charges [Line Items]
Foreign currency exchange rate | VEF / $									13.5			13.5
Foreign currency exchange rate per US dollar, description												13.5 Venezuelan bolivars to one U.S. dollar
International Brotherhood of Teamsters
Special Charges [Line Items]
Severance and benefits costs										83,000,000
Severance and benefits costs net of tax										53,000,000
Int'l Association of Machinists
Special Charges [Line Items]
Curtailment gain recognition of prior service credit											60,000,000
Curtailment gain recognition of prior service credit,net of tax											$ 38,000,000
Number of new contracts extended | Contract											7
Service contract extended year											2,021
Labor agreement costs											$ 171,000,000
Labor agreement costs net of tax											$ 110,000,000
Voluntary early out program
Special Charges [Line Items]
Number of positions eliminated | Attendant													2,500
Voluntary early out program | Maximum
Special Charges [Line Items]
Severance payment per participant													$ 100,000
Voluntary early out program | International Brotherhood of Teamsters
Special Charges [Line Items]
Number of positions eliminated | Technician				1,000
Voluntary early out program | International Brotherhood of Teamsters | Maximum
Special Charges [Line Items]
Severance payment per participant				$ 100,000
Management Reorganization Initiative
Special Charges [Line Items]
Severance and benefits costs										33,000,000
Severance and benefits costs net of tax										21,000,000
Integration Related
Special Charges [Line Items]
(Gains) losses on sale of assets and other miscellaneous (gains) losses, net												$ 14,000,000
Obsolete Spare Parts Inventory
Special Charges [Line Items]
Impairment of assets										10,000,000
Impairment of assets net of tax										6,000,000
Maintenance Service Agreement
Special Charges [Line Items]
Impairment of assets										15,000,000
Impairment of assets net of tax										$ 10,000,000

Schedule of Severance Related A

Schedule of Severance Related Accrual (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Severance and Benefits Costs
Schedule Of Accrual Activity [Line Items]
Beginning Balance	$ 14	$ 27	$ 109
Accrual	116	37	107
Payments	(93)	(50)	(189)
Ending Balance	37	14	27
Permanently Grounded Aircraft
Schedule Of Accrual Activity [Line Items]
Beginning Balance	41	78	102
Accrual	(4)	(17)	30
Payments	(15)	(20)	(54)
Ending Balance	$ 22	$ 41	$ 78

Segment Information - Additiona

Segment Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017Segment
Segment Reporting Information [Line Items]
Number of Operating Segments	1

Operating Revenue by Principle

Operating Revenue by Principle Geographic Region (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total revenues	$ 9,438	$ 9,878	$ 10,000	$ 8,420	$ 9,052	$ 9,913	$ 9,396	$ 8,195	$ 37,736	$ 36,556	$ 37,864
Domestic (U.S. and Canada)
Segment Reporting Information [Line Items]
Total revenues									23,131	22,202	21,931
Pacific
Segment Reporting Information [Line Items]
Total revenues									4,898	4,959	5,498
Atlantic
Segment Reporting Information [Line Items]
Total revenues									6,285	6,157	7,068
Latin America
Segment Reporting Information [Line Items]
Total revenues									$ 3,422	$ 3,238	$ 3,367

Schedule of Selected Quarterly

Schedule of Selected Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Selected Quarterly Financial Data [Line Items]
Operating revenue	$ 9,438	$ 9,878	$ 10,000	$ 8,420	$ 9,052	$ 9,913	$ 9,396	$ 8,195	$ 37,736	$ 36,556	$ 37,864
Income from operations	729	1,092	1,399	278	1,005	1,624	1,060	649	3,498	4,338	5,166
Net income	$ 580	$ 637	$ 818	$ 96	$ 397	$ 965	$ 588	$ 313	$ 2,131	$ 2,263	$ 7,340
Basic earnings per share	$ 1.99	$ 2.12	$ 2.67	$ 0.31	$ 1.26	$ 3.02	$ 1.78	$ 0.88	$ 7.04	$ 6.86	$ 19.52
Diluted earnings per share	$ 1.99	$ 2.12	$ 2.66	$ 0.31	$ 1.26	$ 3.01	$ 1.78	$ 0.88	$ 7.02	$ 6.85	$ 19.47

Schedule of Effect of Four Quar

Schedule of Effect of Four Quarters Events (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating:
Severance and benefit costs	$ 15	$ 23	$ 41	$ 37	$ 10	$ 13	$ 6	$ 8	$ 116	$ 37	$ 107
Impairment of assets	10	15					412		25	412	79
(Gains) losses on sale of assets and other special charges	6	12	3	14	19	18	6	8	35	51	122
Total operating special charges	31	50	44	51	(31)	45	434	190	176	638	326
Labor agreement costs and related items					(60)	14	10	100		64	18
Income taxes:
Income tax benefit related to special charges	(11)	(18)	(16)	(18)	12	(16)	(153)	(72)	(63)	(229)	(11)
Income tax adjustments (Note 7)	(192)				180				(192)	180	(3,130)
Total operating and nonoperating special charges, net of income taxes and income tax adjustments	(172)	32	28	33	161	29	272	126	(79)	588	(2,613)
Cleveland airport lease restructuring								74		74
Severance and benefit costs	15	23	41	37	10	13	6	8	116	37	107
Impairment of assets	10	15					412		25	412	79
(Gains) losses on sale of assets and other special charges	6	12	3	14	19	18	6	8	35	51	122
Total operating special charges	31	50	44	51	(31)	45	434	190	176	638	326
Nonoperating income (expense):
Losses (gain) on extinguishment of debt and other							(9)	8		(1)	202
Income tax expense (benefit) related to special charges	(11)	(18)	(16)	(18)	12	(16)	(153)	(72)	(63)	(229)	(11)
Income tax adjustments (Note 6)	(192)				180				(192)	180	(3,130)
Total operating and nonoperating special charges, net of income taxes and income tax adjustments	$ (172)	$ 32	$ 28	$ 33	$ 161	$ 29	$ 272	$ 126	$ (79)	$ 588	$ (2,613)

Valuation and Qualifying Accoun

Valuation and Qualifying Accounts (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation allowance for deferred tax assets
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		$ 68	$ 48	$ 4,751
Additions Charged to Costs and Expenses		11	47
Deductions	[1]	27	27	4,703
Other		11
Balance at End of Period		63	68	48
UAL and United | Allowance for doubtful accounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		10	18	22
Additions Charged to Costs and Expenses		20	18	25
Deductions	[1]	23	26	29
Balance at End of Period		7	10	18
UAL and United | Obsolescence allowance-spare parts
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		295	235	169
Additions Charged to Costs and Expenses		75	61	38
Deductions	[1]	17	16
Other		1	15	28
Balance at End of Period		354	295	235
United Airlines, Inc. | Valuation allowance for deferred tax assets
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		68	48	4,721
Additions Charged to Costs and Expenses		11	47
Deductions	[1]	27	27	4,673
Other		11
Balance at End of Period		$ 63	$ 68	$ 48
[1]	Deduction from reserve for purpose for which reserve was created.