United Airlines (UAL) 10-K 24 Feb 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2019	Feb. 18, 2020	Jun. 28, 2019
Document Information [Line Items]
Document Type	10-K
Document Fiscal Period Focus	FY
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Amendment Flag	false
Document Fiscal Year Focus	2019
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0000100517
Entity File Number	001-06033
Entity Registrant Name	United Airlines Holdings, Inc.
Entity Address, Address Line One	233 South Wacker Drive,
Entity Address, City or Town	Chicago,
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60606
City Area Code	(872)
Local Phone Number	825-4000
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	36-2675207
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	UAL
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 21.1
Entity Common Stock, Shares Outstanding		247,951,116
Documents Incorporated by Reference	Certain information required by Items 10, 11, 12 and 13 of Part III of this Form 10-K is incorporated by reference for United Airlines Holdings, Inc. from its definitive proxy statement for its 2020 Annual Meeting of Stockholders.
United Airlines, Inc.
Document Information [Line Items]
Entity Central Index Key	0000319687
Entity File Number	001-10323
Entity Registrant Name	United Airlines, Inc.
Entity Address, Address Line One	233 South Wacker Drive,
Entity Address, City or Town	Chicago,
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60606
City Area Code	(872)
Local Phone Number	825-4000
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	74-2099724
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		1,000

Statements of Consolidated Oper

Statements of Consolidated Operations - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Operating revenue:
Revenue	$ 43,259	$ 41,303	[1]	$ 37,784	[1]
Operating expense:
Salaries and related costs	12,071	11,458	[1]	10,941	[1]
Aircraft fuel	8,953	9,307	[1]	6,913	[1]
Regional capacity purchase	2,849	2,649	[1]	2,268	[1]
Landing fees and other rent	2,543	2,449	[1]	2,310	[1]
Depreciation and amortization	2,288	2,165	[1],[2]	2,096	[1],[2]
Aircraft maintenance materials and outside repairs	1,794	1,767	[1]	1,856	[1]
Distribution expenses	1,651	1,558	[1]	1,435	[1]
Aircraft rent	288	433	[1]	621	[1]
Special charges	246	487	[1]	176	[1]
Other operating expenses	6,275	5,801	[1]	5,550	[1]
Total operating expense	38,958	38,074	[1]	34,166	[1]
Operating income	4,301	3,229	[1]	3,618	[1]
Nonoperating income (expense):
Interest expense	(731)	(670)	[1]	(626)	[1]
Interest capitalized	85	65	[1]	74	[1]
Interest income	133	101	[1]	57	[1]
Unrealized gains (losses) on investments, net	153	(5)	[1],[2]	0	[1],[2]
Miscellaneous, net	(27)	(72)	[1]	(100)	[1]
Total nonoperating expense, net	(387)	(581)	[1]	(595)	[1]
Income before income taxes	3,914	2,648	[1]	3,023	[1]
Income tax expense	905	526	[1]	880	[1]
Net income	$ 3,009	$ 2,122	[1],[2],[3],[4]	$ 2,143	[1],[2],[3],[4]
Earnings per share, basic (in dollars per share)	$ 11.63	$ 7.70	[1]	$ 7.08	[1]
Earnings per share, diluted (in dollars per share)	$ 11.58	$ 7.67	[1]	$ 7.06	[1]
United Airlines, Inc.
Operating revenue:
Revenue	$ 43,259	$ 41,303	[5]	$ 37,784	[5]
Operating expense:
Salaries and related costs	12,071	11,458	[5]	10,941	[5]
Aircraft fuel	8,953	9,307	[5]	6,913	[5]
Regional capacity purchase	2,849	2,649	[5]	2,268	[5]
Landing fees and other rent	2,543	2,449	[5]	2,310	[5]
Depreciation and amortization	2,288	2,165	[5],[6]	2,096	[5],[6]
Aircraft maintenance materials and outside repairs	1,794	1,767	[5]	1,856	[5]
Distribution expenses	1,651	1,558	[5]	1,435	[5]
Aircraft rent	288	433	[5]	621	[5]
Special charges	246	487	[5]	176	[5]
Other operating expenses	6,273	5,799	[5]	5,548	[5]
Total operating expense	38,956	38,072	[5]	34,164	[5]
Operating income	4,303	3,231	[5]	3,620	[5]
Nonoperating income (expense):
Interest expense	(731)	(670)	[5]	(626)	[5]
Interest capitalized	85	65	[5]	74	[5]
Interest income	133	101	[5]	57	[5]
Unrealized gains (losses) on investments, net	153	(5)	[5],[6]	0	[5],[6]
Miscellaneous, net	(27)	(72)	[5]	(100)	[5]
Total nonoperating expense, net	(387)	(581)	[5]	(595)	[5]
Income before income taxes	3,916	2,650	[5]	3,025	[5]
Income tax expense	905	527	[5]	864	[5]
Net income	3,011	2,123	[5],[6],[7],[8]	2,161	[5],[6],[7],[8]
Passenger revenue
Operating revenue:
Revenue	39,625	37,706	[1]	34,460	[1]
Passenger revenue | United Airlines, Inc.
Operating revenue:
Revenue	39,625	37,706	[5]	34,460	[5]
Cargo
Operating revenue:
Revenue	1,179	1,237	[1]	1,114	[1]
Cargo | United Airlines, Inc.
Operating revenue:
Revenue	1,179	1,237	[5]	1,114	[5]
Other operating revenue
Operating revenue:
Revenue	2,455	2,360	[1]	2,210	[1]
Other operating revenue | United Airlines, Inc.
Operating revenue:
Revenue	$ 2,455	$ 2,360	[5]	$ 2,210	[5]
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[2]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[3]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8
[4]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[5]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[6]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[7]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[8]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Statements of Consolidated Comp

Statements of Consolidated Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Net income	$ 3,009	$ 2,122	[1],[2],[3],[4]	$ 2,143	[1],[2],[3],[4]
Other comprehensive income (loss), net of tax:
Employee benefit plans	80	342	[2]	(195)	[2]
Investments and other	5	(4)	[2]	(5)	[2]
Total other comprehensive income (loss), net of tax	85	338	[2]	(200)	[2]
Total comprehensive income, net	3,094	2,460	[2]	1,943	[2]
United Airlines, Inc.
Net income	3,011	2,123	[5],[6],[7],[8]	2,161	[5],[6],[7],[8]
Other comprehensive income (loss), net of tax:
Employee benefit plans	80	342	[6]	(195)	[6]
Investments and other	5	(4)	[6]	(5)	[6]
Total other comprehensive income (loss), net of tax	85	338	[6]	(200)	[6]
Total comprehensive income, net	$ 3,096	$ 2,461	[6]	$ 1,961	[6]
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8
[2]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[3]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[4]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[5]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[6]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[7]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[8]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 2,762	$ 1,694	[1]
Short-term investments	2,182	2,256	[1]
Receivables, less allowance for doubtful accounts (2019—$9; 2018—$8)	1,364	1,426	[1]
Aircraft fuel, spare parts and supplies, less obsolescence allowance (2019—$425; 2018—$412)	1,072	985	[1]
Prepaid expenses and other	814	733	[1]
Total current assets	8,194	7,094	[1]
Operating property and equipment:
Flight equipment	35,421	32,599	[1]
Other property and equipment	7,926	6,889	[1]
Purchase deposits for flight equipment	1,360	1,177	[1]
Total operating property and equipment	44,707	40,665	[1]
Less—Accumulated depreciation and amortization	(14,537)	(13,266)	[1]
Total operating property and equipment, net	30,170	27,399	[1]
Operating lease right-of-use assets	4,758	5,262	[1]
Other assets:
Goodwill	4,523	4,523	[1]
Intangibles, less accumulated amortization (2019—$1,440; 2018—$1,380)	3,009	3,159	[1]
Restricted cash	106	105	[1]
Notes receivable, net	671	516	[1]
Investments in affiliates and other, net	1,180	966	[1]
Total other assets	9,489	9,269	[1]
Total assets	52,611	49,024	[1]
Current liabilities:
Advance ticket sales	4,819	4,381	[1]
Accounts payable	2,703	2,363	[1]
Frequent flyer deferred revenue	2,440	2,286	[1]
Accrued salaries and benefits	2,271	2,184	[1]
Current maturities of long-term debt	1,407	1,230	[1]
Current maturities of finance leases	46	123	[1]
Current maturities of operating leases	686	719	[1]
Other	566	553	[1]
Total current liabilities	14,938	13,839	[1]
Long-term debt	13,145	12,215	[1]
Long-term obligations under finance leases	220	224	[1]
Long-term obligations under operating leases	4,946	5,276	[1]
Other liabilities and deferred credits:
Frequent flyer deferred revenue	2,836	2,719	[1]
Postretirement benefit liability	789	1,295	[1]
Pension liability	1,446	1,576	[1]
Deferred income taxes	1,736	828	[1]
Other	1,024	1,010	[1]
Total other liabilities and deferred credits	7,831	7,428	[1]
Commitments and contingencies			[1]
Stockholders' equity:
Preferred stock	0	0	[1]
Common stock	3	3	[1]
Additional capital invested	6,129	6,120	[1]
Stock held in treasury, at cost	(3,599)	(1,993)	[1]
Retained earnings	9,716	6,715	[1]
Accumulated other comprehensive loss	(718)	(803)	[1]
Total stockholders' equity	11,531	10,042	[1]
Total liabilities and stockholders' equity	52,611	49,024	[1]
United Airlines, Inc.
Current assets:
Cash and cash equivalents	2,756	1,688	[2]
Short-term investments	2,182	2,256	[2]
Receivables, less allowance for doubtful accounts (2019—$9; 2018—$8)	1,364	1,426	[2]
Aircraft fuel, spare parts and supplies, less obsolescence allowance (2019—$425; 2018—$412)	1,072	985	[2]
Prepaid expenses and other	814	733	[2]
Total current assets	8,188	7,088	[2]
Operating property and equipment:
Flight equipment	35,421	32,599	[2]
Other property and equipment	7,926	6,889	[2]
Purchase deposits for flight equipment	1,360	1,177	[2]
Total operating property and equipment	44,707	40,665	[1]
Less—Accumulated depreciation and amortization	(14,537)	(13,266)	[1]
Total operating property and equipment, net	30,170	27,399	[1]
Operating lease right-of-use assets	4,758	5,262	[2]
Other assets:
Goodwill	4,523	4,523	[2]
Intangibles, less accumulated amortization (2019—$1,440; 2018—$1,380)	3,009	3,159	[2]
Restricted cash	106	105	[2]
Notes receivable, net	671	516	[2]
Investments in affiliates and other, net	1,180	966	[2]
Total other assets	9,489	9,269	[2]
Total assets	52,605	49,018	[2]
Current liabilities:
Advance ticket sales	4,819	4,381	[2]
Accounts payable	2,703	2,363	[2]
Frequent flyer deferred revenue	2,440	2,286	[2]
Accrued salaries and benefits	2,271	2,184	[2]
Current maturities of long-term debt	1,407	1,230	[2]
Current maturities of finance leases	46	123	[2]
Current maturities of operating leases	686	719	[2]
Other	571	558	[2]
Total current liabilities	14,943	13,844	[2]
Long-term debt	13,145	12,215	[2]
Long-term obligations under finance leases	220	224	[2]
Long-term obligations under operating leases	4,946	5,276	[2]
Other liabilities and deferred credits:
Frequent flyer deferred revenue	2,836	2,719	[2]
Postretirement benefit liability	789	1,295	[2]
Pension liability	1,446	1,576	[2]
Deferred income taxes	1,763	855	[2]
Other	1,025	1,010	[2]
Total other liabilities and deferred credits	7,859	7,455	[2]
Commitments and contingencies			[2]
Stockholders' equity:
Common stock	0	0	[2]
Additional capital invested	0	598	[2]
Retained earnings	12,353	10,319	[2]
Accumulated other comprehensive loss	(718)	(803)	[2]
Receivable from related parties	(143)	(110)	[2]
Total stockholders' equity	11,492	10,004	[2]
Total liabilities and stockholders' equity	$ 52,605	$ 49,018	[2]
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[2]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Receivables, allowance for doubtful accounts	$ 9	$ 8	[1]
Aircraft fuel, spare parts and supplies, obsolescence allowance	425	412	[1]
Intangibles, accumulated amortization	$ 1,440	$ 1,380	[1]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	[1]
Common shares, authorized (in shares)	1,000,000,000	1,000,000,000	[1]
Common shares, outstanding (in shares)	251,216,381	269,914,769	[1]
United Airlines, Inc.
Receivables, allowance for doubtful accounts	$ 9	$ 8	[2]
Aircraft fuel, spare parts and supplies, obsolescence allowance	425	412	[2]
Intangibles, accumulated amortization	$ 1,440	$ 1,380	[2]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	[2]
Common shares, authorized (in shares)	1,000	1,000	[2]
Common shares, issued (in shares)	1,000	1,000	[2]
Common shares, outstanding (in shares)	1,000	1,000	[2]
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[2]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Statements of Consolidated Cash

Statements of Consolidated Cash Flows - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Operating Activities:
Net income		$ 3,009	$ 2,122	[1],[2],[3],[4]	$ 2,143	[1],[2],[3],[4]
Adjustments to reconcile net income to net cash provided by operating activities -
Deferred income taxes		882	512	[3]	957	[3]
Depreciation and amortization		2,288	2,165	[3],[4]	2,096	[3],[4]
Special charges, non-cash portion		175	416	[3]	35	[3]
Unrealized (gains) losses on investments		(153)	5	[3],[4]	0	[3],[4]
Other operating activities		185	161	[3]	142	[3]
Changes in operating assets and liabilities -
(Increase) decrease in receivables		44	17	[3]	(73)	[3]
(Increase) decrease in other assets		(252)	265	[3]	(432)	[3]
Increase in advance ticket sales		438	441	[3]	145	[3]
Increase (decrease) in frequent flyer deferred revenue		271	222	[3]	(107)	[3]
Increase in accounts payable		324	130	[3]	66	[3]
Decrease in advanced purchase of miles		0	0	[3]	(942)	[3]
Decrease in other liabilities		(302)	(292)	[3]	(556)	[3]
Net cash provided by operating activities		6,909	6,164	[3]	3,474	[3]
Investing Activities:
Capital expenditures		(4,528)	(4,070)	[3]	(3,870)	[3]
Purchases of short-term and other investments		(2,897)	(2,552)	[3]	(3,241)	[3]
Proceeds from sale of short-term and other investments		2,996	2,616	[3]	3,177	[3]
Loans made to others		(174)	(466)	[3]	(30)	[3]
Investment in affiliates		(36)	(139)	[3]	(2)	[3]
Other, net		79	156	[3]	163	[3]
Net cash used in investing activities		(4,560)	(4,455)	[3]	(3,803)	[3]
Financing Activities:
Repurchases of common stock		(1,645)	(1,235)	[3]	(1,844)	[3]
Proceeds from issuance of long-term debt		1,847	1,594	[3]	2,537	[3]
Payments of long-term debt		(1,240)	(1,727)	[3]	(901)	[3]
Principal payments under finance leases		(151)	(79)	[3]	(84)	[3]
Capitalized financing costs		(61)	(37)	[3]	(80)	[3]
Other, net		(30)	(17)	[3]	(11)	[3]
Net cash used in financing activities		(1,280)	(1,501)	[3]	(383)	[3]
Net increase (decrease) in cash, cash equivalents and restricted cash		1,069	208	[3]	(712)	[3]
Cash, cash equivalents and restricted cash at beginning of year	[3]	1,799	1,591		2,303
Cash, cash equivalents and restricted cash at end of year		2,868	1,799	[3]	1,591	[3]
Investing and Financing Activities Not Affecting Cash:
Property and equipment acquired through the issuance of debt		493	143	[3]	897	[3]
Right-of-use assets acquired through operating leases		498	663	[3]	319	[3]
Property and equipment acquired through finance lease		22	17	[3]	16	[3]
Lease modifications and lease conversions		(2)	52	[3]	0	[3]
Debt associated with termination of a maintenance service agreement		0	163	[3]	0	[3]
Investment in Republic Airways Holdings Inc. received from bankruptcy claims		0	0	[3]	92	[3]
Cash Paid During the Period for:
Interest		648	651	[3]	571	[3]
Income taxes		29	19	[3]	20	[3]
United Airlines, Inc.
Operating Activities:
Net income		3,011	2,123	[5],[6],[7],[8]	2,161	[5],[6],[7],[8]
Adjustments to reconcile net income to net cash provided by operating activities -
Deferred income taxes		882	513	[5]	941	[5]
Depreciation and amortization		2,288	2,165	[5],[7]	2,096	[5],[7]
Special charges, non-cash portion		175	416	[5]	35	[5]
Unrealized (gains) losses on investments		(153)	5	[5],[7]	0	[5],[7]
Other operating activities		186	162	[5]	141	[5]
Changes in operating assets and liabilities -
(Increase) decrease in receivables		44	17	[5]	(73)	[5]
Increase in intercompany receivables		(33)	(20)	[5]	(15)	[5]
(Increase) decrease in other assets		(252)	265	[5]	(432)	[5]
Increase in advance ticket sales		438	441	[5]	145	[5]
Increase (decrease) in frequent flyer deferred revenue		271	222	[5]	(107)	[5]
Increase in accounts payable		324	130	[5]	66	[5]
Decrease in advanced purchase of miles		0	0	[5]	(942)	[5]
Decrease in other liabilities		(302)	(293)	[5]	(556)	[5]
Net cash provided by operating activities		6,879	6,146	[5]	3,460	[5]
Investing Activities:
Capital expenditures		(4,528)	(4,070)	[5]	(3,870)	[5]
Purchases of short-term and other investments		(2,897)	(2,552)	[5]	(3,241)	[5]
Proceeds from sale of short-term and other investments		2,996	2,616	[5]	3,177	[5]
Loans made to others		(174)	(466)	[5]	(30)	[5]
Investment in affiliates		(36)	(139)	[5]	(2)	[5]
Other, net		79	156	[5]	163	[5]
Net cash used in investing activities		(4,560)	(4,455)	[5]	(3,803)	[5]
Financing Activities:
Proceeds from issuance of long-term debt		1,847	1,594	[5]	2,537	[5]
Payments of long-term debt		(1,240)	(1,727)	[5]	(901)	[5]
Dividend to UAL		(1,645)	(1,235)	[5]	(1,844)	[5]
Principal payments under finance leases		(151)	(79)	[5]	(84)	[5]
Capitalized financing costs		(61)	(37)	[5]	(80)	[5]
Other, net		0	1	[5]	3	[5]
Net cash used in financing activities		(1,250)	(1,483)	[5]	(369)	[5]
Net increase (decrease) in cash, cash equivalents and restricted cash		1,069	208	[5]	(712)	[5]
Cash, cash equivalents and restricted cash at beginning of year	[5]	1,793	1,585		2,297
Cash, cash equivalents and restricted cash at end of year		2,862	1,793	[5]	1,585	[5]
Investing and Financing Activities Not Affecting Cash:
Property and equipment acquired through the issuance of debt		493	143	[5]	897	[5]
Right-of-use assets acquired through operating leases		498	663	[5]	319	[5]
Property and equipment acquired through finance lease		22	17	[5]	16	[5]
Lease modifications and lease conversions	[5]		52		0
Debt associated with termination of a maintenance service agreement		0	163	[5]	0	[5]
Investment in Republic Airways Holdings Inc. received from bankruptcy claims		0	0	[5]	92	[5]
Cash Paid During the Period for:
Interest		648	651	[5]	571	[5]
Income taxes		$ 29	$ 19	[5]	$ 20	[5]
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8
[2]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[3]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[4]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[5]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[6]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[7]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[8]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Statements of Consolidated Stoc

Statements of Consolidated Stockholder's Equity - USD ($) $ in Millions	Total		United Airlines, Inc.		Common Stock	Additional Capital Invested	Additional Capital InvestedUnited Airlines, Inc.	Treasury Stock	Retained Earnings (Accumulated Deficit)		Retained Earnings (Accumulated Deficit)United Airlines, Inc.		Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss)United Airlines, Inc.	Receivable from Related Parties, NetUnited Airlines, Inc.
Balance (in shares) at Dec. 31, 2016					314,600,000
Balance at Dec. 31, 2016	$ 8,574		$ 8,520		$ 3	$ 6,569	$ 3,573	$ (511)	$ 3,342		$ 5,851		$ (829)	$ (829)	$ (75)
Net income	2,143	[1],[2],[3],[4]	2,161	[5],[6],[7],[8]					2,143	[1]	2,161	[8]
Other comprehensive income	(200)	[2]	(200)	[5]									(200)	(200)
Dividend to UAL			(1,844)				(1,844)
Stock-settled share-based compensation	56		56			56	56
Proceeds from exercise of stock options	2					2
Repurchases of common stock (in shares)					(27,800,000)
Repurchases of common stock	(1,844)							(1,844)
Treasury stock retired	0					(508)		1,576	(1,068)
Net treasury stock issued for share-based awards (in shares)					200,000
Net treasury stock issued for share-based awards	(12)					(21)		10	(1)
Excess tax benefits from share-based awards	14		14						14		14
UAL contribution related to stock plans			2				2
Reclassification of stranded tax effects	0		0						118		118		(118)	(118)
Other	55	[1]	42	[8]					55	[1]	57	[8]			(15)	[8]
Balance (in shares) at Dec. 31, 2017					287,000,000
Balance at Dec. 31, 2017	8,788		8,751		$ 3	6,098	1,787	(769)	4,603		8,201		(1,147)	(1,147)	(90)
Net income	2,122	[1],[2],[3],[4]	2,123	[5],[6],[7],[8]					2,122	[1]	2,123	[8]
Other comprehensive income	338	[2]	338	[5]									338	338
Dividend to UAL			(1,249)				(1,249)
Stock-settled share-based compensation	60		60			60	60
Repurchases of common stock (in shares)					(17,500,000)
Repurchases of common stock	(1,250)							(1,250)
Net treasury stock issued for share-based awards (in shares)					400,000
Net treasury stock issued for share-based awards	$ (16)					(38)		26	(4)
Other			$ (19)								(5)			6	(20)
Balance (in shares) at Dec. 31, 2018	269,914,769	[9]	1,000	[10]	269,900,000
Balance at Dec. 31, 2018	$ 10,042	[9]	$ 10,004	[10]	$ 3	6,120	598	(1,993)	6,715		10,319		(803)	(803)	(110)
Net income	3,009		3,011						3,009		3,011
Other comprehensive income	85		85										85	85
Dividend to UAL			(1,641)				(664)				(977)
Stock-settled share-based compensation	$ 66		66			66	66
Repurchases of common stock (in shares)	(19,200,000)				(19,200,000)
Repurchases of common stock	$ (1,641)							(1,641)
Net treasury stock issued for share-based awards (in shares)					500,000
Net treasury stock issued for share-based awards	$ (30)					(57)		35	(8)
Other			$ (33)												(33)
Balance (in shares) at Dec. 31, 2019	251,216,381		1,000		251,200,000
Balance at Dec. 31, 2019	$ 11,531		$ 11,492		$ 3	$ 6,129	$ 0	$ (3,599)	$ 9,716		$ 12,353		$ (718)	$ (718)	$ (143)
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8
[2]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[3]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[4]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[5]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[6]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[7]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[8]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[9]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[10]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Significant Accounting Policies	SIGNIFICANT ACCOUNTING POLICIES (a) Use of Estimates— The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America ("GAAP") requires management to make estimates and assumptions that affect the amounts reported in these financial statements and accompanying notes. Actual results could differ from those estimates. (b) Revenue Recognition— The Company presents Passenger revenue, Cargo revenue and Other operating revenue on its income statement. Passenger revenue is recognized when transportation is provided and Cargo revenue is recognized when shipments arrive at their destination. Other operating revenue is recognized as the related performance obligations are satisfied. Passenger tickets and related ancillary services sold by the Company for mainline and regional flights are purchased primarily via credit card transactions, with payments collected by the Company in advance of the performance of related services. The Company initially records ticket sales in its Advance ticket sales liability, deferring revenue recognition until the travel occurs. For travel that has more than one flight segment, the Company deems each segment as a separate performance obligation and recognizes revenue for each segment as travel occurs. Tickets sold by other airlines where the Company provides the transportation are recognized as passenger revenue at the estimated value to be billed to the other airline when travel is provided. Differences between amounts billed and the actual amounts may be rejected and rebilled or written off if the amount recorded was different from the original estimate. When necessary, the Company records a reserve against its billings and payables with other airlines based on historical experience. The Company sells certain tickets with connecting flights with one or more segments operated by its other airline partners. For segments operated by its other airline partners, the Company has determined that it is acting as an agent on behalf of the other airlines as they are responsible for their portion of the contract (i.e. transportation of the passenger). The Company, as the agent, recognizes revenue within Other operating revenue at the time of the travel for the net amount representing commission to be retained by the Company for any segments flown by other airlines. Refundable tickets expire after one year from the date of issuance. Non-refundable tickets generally expire on the date of the intended travel, unless the date is extended by notification from the customer on or before the intended travel date. The Company records breakage revenue on the travel date for its estimate of tickets that will expire unused. To determine breakage, the Company uses its historical experience with refundable and nonrefundable expired tickets and other facts, such as recent aging trends, program changes and modifications that could affect the ultimate expiration patterns of tickets. Fees charged in association with changes or extensions to non-refundable tickets are considered part of the Company's passenger travel obligation. As such, those fees are deferred at the time of collection and recognized at the time the travel is provided. United initially capitalizes the costs of selling airline travel tickets and then recognizes those costs as Distribution expense at the time of travel. Passenger ticket costs include credit card fees, travel agency and other commissions paid, as well as global distribution systems booking fees. Advance Ticket Sales. Advance ticket sales represent the Company's liability to provide air transportation in the future. In the years ended December 31, 2019 and 2018 , the Company recognized approximately $3.4 billion and $3.1 billion , respectively, of passenger revenue for tickets that were included in Advance ticket sales at the beginning of those periods. All tickets sold at any given point of time have travel dates extending up to 12 months. As a result, the balance of the Company's Advance ticket sales liability represents activity that will be recognized in the next 12 months. Revenue by Geography. The Company further disaggregates revenue by geographic regions. 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): 2019 2018 2017 Domestic (U.S. and Canada) $ 26,960 $ 25,552 $ 23,114 Atlantic 7,387 7,103 6,340 Pacific 5,132 5,188 4,914 Latin America 3,780 3,460 3,416 Total $ 43,259 $ 41,303 $ 37,784 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. Ancillary Fees. The Company charges fees, separately from ticket sales, for certain ancillary services that are directly related to passengers' travel, such as ticket change fees, baggage fees, inflight amenities fees, and other ticket-related fees. These ancillary fees are part of the travel performance obligation and, as such, are recognized as passenger revenue when the travel occurs. The Company recorded $2.4 billion , $2.2 billion , and $2.0 billion of ancillary fees within passenger revenue in the years ended December 31, 2019 , 2018 and 2017 , respectively. (c) Ticket Taxes— Certain governmental taxes are imposed on the Company's ticket sales through a fee included in ticket prices. The Company collects these fees and remits them to the appropriate government agency. These fees are recorded on a net basis and, as a result, are excluded from revenue. (d) Frequent Flyer Accounting— United's MileagePlus loyalty program builds customer loyalty by offering awards, benefits and services to program participants. Members in this program earn miles for travel on United, United Express, Star Alliance members and certain other airlines that participate in the program. Members can also earn miles by purchasing goods and services from our network of non-airline partners. We have contracts to sell miles to these partners with the terms extending from one to nine years . These partners include domestic and international credit card issuers, retail merchants, hotels, car rental companies and our participating airline partners. Miles can be redeemed for free (other than taxes and government-imposed fees), discounted or upgraded air travel and non-travel awards. Miles Earned in Conjunction with Travel. When frequent flyers earn miles for flights, the Company recognizes a portion of the ticket sales as revenue when the travel occurs and defers a portion of the ticket sale representing the value of the related miles as a separate performance obligation. The Company determines the estimated selling price of travel 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. At the time of travel, the Company records the portion allocated to the miles to Frequent flyer deferred revenue on the Company's consolidated balance sheet and subsequently recognizes it into revenue when miles are redeemed for air travel and non-air travel awards. Estimate of Miles Not Expected to be Redeemed . The Company's estimated selling price of miles is based on an equivalent ticket value less breakage, 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 breakage that considers a number of factors, including redemption patterns of various customer groups. The Company's breakage model is based on the assumption that the likelihood that an account will redeem its miles can be estimated based on a consideration of the account's historical behavior. The Company uses a logit regression model to estimate the probability that an account will redeem its current miles balance. The Company reviews its breakage estimates annually based upon the latest available information. The Company's estimate of the expected breakage of miles requires significant management judgment. Current and future changes to breakage assumptions, 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 program. For the portion of the outstanding miles that we estimate will not be redeemed, we recognize the associated value proportionally as the remaining miles are redeemed. Co-Brand Agreement . United has a significant contract (the "Co-Brand Agreement") to sell MileagePlus miles to its co-branded credit card partner JPMorgan Chase Bank, N.A. ("Chase"). Chase awards miles to MileagePlus members based on their credit card activity. United identified the following significant separately identifiable performance obligations in the Co-Brand Agreement: • MileagePlus miles awarded – United has a performance obligation to provide MileagePlus cardholders with miles to be used for air travel and non-travel award redemptions. The Company records Passenger revenue related to the travel awards when the transportation is provided and records Other revenue related to the non-travel awards when the goods or services are delivered. The Company records the cost associated with non-travel awards in Other operating revenue. • Marketing – United has a performance obligation to provide Chase access to United's customer list and the use of United's brand. Marketing revenue is recorded to Other operating revenue as miles are delivered to Chase. • Advertising – United has a performance obligation to provide advertising in support of the MileagePlus card in various customer contact points such as United's website, email promotions, direct mail campaigns, airport advertising and in-flight advertising. Advertising revenue is recorded to Other operating revenue as miles are delivered to Chase. • Other travel-related benefits – United's performance obligations are comprised of various items such as waived bag fees, seat upgrades and lounge passes. Lounge passes are recorded to Other operating revenue as customers use the lounge passes. Bag fees and seat upgrades are recorded to Passenger revenue at the time of the associated travel. We account for all the payments received (including monthly and one-time payments) under the Co-Brand Agreement by allocating them to the separately identifiable performance obligations. The fair value of the separately identifiable performance obligations is determined using management's estimated selling price of each component. 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 Agreement in order to determine the allocation of proceeds to each of the components to be delivered. We also evaluate volumes on an annual basis, which may result in a change in the allocation of the estimated consideration from the Co-Brand Agreement on a prospective basis. Frequent Flyer Deferred Revenue. Miles in MileagePlus members' accounts are combined into one homogeneous pool and are thus not separately identifiable, for award redemption purposes, between miles earned in the current period and those in their beginning balance. Of the miles expected to be redeemed, the Company expects the majority of these miles to be redeemed within two years . The table below presents a roll forward of Frequent flyer deferred revenue (in millions): Twelve Months Ended 2019 2018 Total Frequent flyer deferred revenue - beginning balance $ 5,005 $ 4,783 Total miles awarded 2,621 2,451 Travel miles redeemed (Passenger revenue) (2,213 ) (2,068 ) Non-travel miles redeemed (Other operating revenue) (137 ) (161 ) Total Frequent flyer deferred revenue - ending balance $ 5,276 $ 5,005 In the years ended December 31, 2019 , 2018 and 2017 , the Company recognized, in Other operating revenue, $2.0 billion , $2.0 billion (including a one-time $50 million payment) and $1.8 billion , respectively, related to the marketing, advertising, non-travel miles redeemed (net of related costs) and other travel-related benefits of the mileage revenue associated with our various partner agreements including, but not limited to, our Chase co-brand agreement. The portion related to the MileagePlus miles awarded of the total amounts received is deferred and presented in the table above as an increase to the frequent flyer liability. (e) Cash and Cash Equivalents and Restricted Cash— Highly liquid investments with a maturity of three months or less on their acquisition date are classified as cash and cash equivalents. Restricted cash primarily includes cash collateral for letters of credit and collateral associated with obligations for facility leases and other insurance-related obligations. 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 (in millions): UAL United At December 31, At December 31, 2019 2018 2017 2019 2018 2017 Current assets: Cash and cash equivalents $ 2,762 $ 1,694 $ 1,482 $ 2,756 $ 1,688 $ 1,476 Restricted cash included in Prepaid expenses and other — — 18 — — 18 Other assets: Restricted cash 106 105 91 106 105 91 Total cash, cash equivalents and restricted cash shown in the statement of consolidated cash flows $ 2,868 $ 1,799 $ 1,591 $ 2,862 $ 1,793 $ 1,585 (f) Investments— Debt investments are classified as available-for-sale and are stated at fair value. Realized gains and losses on sales of these investments are reflected in Miscellaneous, net in the consolidated statements of operations. Unrealized gains and losses on available-for-sale securities are reflected as a component of accumulated other comprehensive income (loss). Equity investments with readily determinable fair values are measured at fair value. Equity investments without readily determinable fair values are measured using the equity method, or measured at cost with adjustments for observable changes in price or impairments (referred to as the measurement alternative). Changes in fair value are recorded in Unrealized gains (losses) on investments, net in the consolidated statements of operations. (g) Accounts Receivable— Accounts receivable primarily consist of amounts due from credit card companies, non-airline partners, and cargo transportation customers. 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 year ended December 31, 2019 and 2018 . (h) Aircraft Fuel, Spare Parts and Supplies— The Company accounts for aircraft fuel, spare parts and supplies at average cost and provides an obsolescence allowance for aircraft spare parts with an assumed residual value of 10% of original cost. (i) Property and Equipment— The Company records additions to owned operating property and equipment at cost when acquired. Property under finance leases and the related obligation for future lease payments are recorded at an amount equal to the initial present value of those lease payments. Modifications that enhance the operating performance or extend the useful lives of airframes or engines are capitalized as property and equipment. It is the Company's policy to record contractual damages received related to delays in delivery of aircraft as a reduction of the cost of the related aircraft. 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 certain at key airports, or the estimated useful life of the related asset, whichever is less. Properties under finance 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 finance 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, spare engines and related rotable parts 25 to 30 Aircraft seats 10 to 15 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, 2019 and 2018 , the Company had a carrying value of computer software of $422 million and $359 million , respectively. For the years ended December 31, 2019 , 2018 and 2017 , the Company's depreciation expense related to computer software was $135 million , $122 million and $117 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. (j) Long-Lived Asset Impairments— The Company evaluates the carrying value of long-lived assets subject to amortization whenever events or changes in circumstances indicate that an impairment may exist. For purposes of this testing, the Company has generally identified the aircraft fleet type as the lowest level of identifiable cash flows. An impairment charge is recognized when the asset's carrying value exceeds its net undiscounted future cash flows and its fair market value. The amount of the charge is the difference between the asset's carrying value and fair market value. See Note 14 of this report for additional information related to impairments. (k) Intangibles— The Company has finite-lived and indefinite-lived intangible assets, including goodwill. Finite-lived intangible assets are amortized over their estimated useful lives. Goodwill and indefinite-lived intangible assets are not amortized but are reviewed for impairment on an annual basis as of October 1, or more frequently if events or circumstances indicate that the asset may be impaired. See Note 14 of this report for additional information related to impairments. The following table presents information about the Company's goodwill and other intangible assets at December 31 (in millions): 2019 2018 Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Goodwill $ 4,523 $ 4,523 Indefinite-lived intangible assets Route authorities $ 1,150 $ 1,240 Airport slots 546 546 Tradenames and logos 593 593 Alliances 404 404 Total $ 2,693 $ 2,783 Finite-lived intangible assets Frequent flyer database $ 1,177 $ 931 $ 1,177 $ 884 Hubs 145 104 145 97 Contracts 120 111 120 106 Other 314 294 314 293 Total $ 1,756 $ 1,440 $ 1,756 $ 1,380 Amortization expense in 2019 , 2018 and 2017 was $60 million , $67 million and $79 million , respectively. Projected amortization expense in 2020 , 2021 , 2022 , 2023 and 2024 is $55 million , $50 million , $40 million , $37 million and $32 million , respectively. (l) Labor Costs— The Company records expenses associated with new or amendable labor agreements when the amounts are probable and estimable. These include costs associated with lump sum cash payments that would be made in conjunction with the ratification of labor agreements. To the extent these upfront costs are in lieu of future pay increases, they would be capitalized and amortized over the term of the labor agreements. If not, these amounts would be expensed. (m) Share-Based Compensation— The Company measures the cost of employee services received in exchange for an award of equity instruments based on the grant date fair value of the award. The resulting cost is recognized over the period during which an employee is required to provide service in exchange for the award, usually the vesting period. Obligations for cash-settled restricted stock units ("RSUs") are remeasured at fair value throughout the requisite service period at the close of the reporting period based upon UAL's stock price. In addition to the service requirement, certain RSUs have performance metrics that must be achieved prior to vesting. These awards are accrued based on the expected level of achievement at each reporting period. An adjustment is recorded each reporting period to adjust compensation expense based on the then current level of expected performance achievement for the performance-based awards. See Note 4 of this report for additional information on UAL's share-based compensation plans. (n) Maintenance and Repairs— The cost of maintenance and repairs, including the cost of minor replacements, is charged to expense as incurred, except for costs incurred under our power-by-the-hour ("PBTH") engine maintenance agreements. PBTH contracts transfer certain risk to third-party service providers and fix the amount we pay per flight hour or per cycle to the service provider in exchange for maintenance and repairs under a predefined maintenance program. Under PBTH agreements, the Company recognizes expense at a level rate per engine hour, unless the level of service effort and the related payments during the period are substantially consistent, in which case the Company recognizes expense based on the amounts paid. (o) Advertising— Advertising costs, which are included in Other operating expenses, are expensed as incurred. Advertising expenses were $212 million , $211 million and $217 million for the years ended December 31, 2019 , 2018 and 2017 , respectively. (p) Third-Party Business— The Company has third-party business revenue that includes fuel sales, catering, ground handling, maintenance services and frequent flyer award non-travel redemptions. Third-party business revenue is recorded in Other operating revenue. The Company also incurs third-party business expenses, such as maintenance, ground handling and catering services for third parties, fuel sales and non-travel mileage redemptions. The third-party business expenses are recorded in Other operating expenses, except for non-travel mileage redemption. Non-travel mileage redemption expenses are recorded to Other operating revenue. (q) Uncertain Income Tax Positions— The Company has recorded reserves for income taxes and associated interest that may become payable in future years. Although management believes that its positions taken on income tax matters are reasonable, the Company nevertheless has established tax and interest reserves in recognition that various taxing authorities may challenge certain of the positions taken by the Company, potentially resulting in additional liabilities for taxes and interest. The Company's uncertain tax position reserves are reviewed periodically and are adjusted as events occur that affect its estimates, such as the availability of new information, the lapsing of applicable statutes of limitation, the conclusion of tax audits, the measurement of additional estimated liability, the identification of new tax matters, the release of administrative tax guidance affecting its estimates of tax liabilities, or the rendering of relevant court decisions. The Company records penalties and interest relating to uncertain tax positions as part of income tax expense in its consolidated statements of operations. See Note 6 of this report for additional information on UAL's uncertain tax positions. (r) Recently Issued Accounting Standards— The Company adopted Financial Accounting Standards Board ("FASB") Accounting Standards Codification Topic 842, Leases (the "New Lease Standard"), effective January 1, 2019. The Company used the modified retrospective approach for all leases existing at or commencing after January 1, 2017 and elected the package of transition practical expedients for expired or existing contracts, which does not require reassessment of: (1) whether any of our contracts are or contain leases, (2) lease classification and (3) initial direct costs. The New Lease Standard prescribes that an entity should recognize a right-of-use asset and a lease liability for all leases at the commencement date of each lease and recognize expenses on their income statements similar to the prior FASB Accounting Standards Codification Topic 840, Leases ("Topic 840"). The adoption of the New Lease Standard had the same impact on the financial statements of United as it had on the financial statements of UAL. The table below presents the impact of the adoption of the New Lease Standard on select accounts and captions of UAL's statement of consolidated operations for the year ended December 31 (in millions, except per share amounts): As Reported New Lease Standard Adjustments As Adjusted 2018 2017 2018 2017 2018 2017 Regional capacity purchase $ 2,601 $ 2,232 $ 48 $ 36 $ 2,649 $ 2,268 Landing fees and other rent 2,359 2,240 90 70 2,449 2,310 Depreciation and amortization 2,240 2,149 (75 ) (53 ) 2,165 2,096 Interest expense (729 ) (671 ) 59 45 (670 ) (626 ) Interest capitalized 70 84 (5 ) (10 ) 65 74 Income tax expense 529 896 (3 ) (16 ) 526 880 Net income 2,129 2,144 (7 ) (1 ) 2,122 2,143 Earnings per share, basic 7.73 7.08 (0.03 ) — 7.70 7.08 Earnings per share, diluted 7.70 7.06 (0.03 ) — 7.67 7.06 The expense for leases under the New Lease Standard will continue to be classified in their historical income statement captions (primarily in Aircraft rent, Landing fees and other rent and Regional capacity purchase in our statements of consolidated operations). The adoption of the New Lease Standard resulted in the recharacterization of certain leases from capital leases under Topic 840 to operating leases under the New Lease Standard. This change resulted in less depreciation and amortization and interest expense associated with capital leases offset by higher lease expense associated with operating leases. The recharacterization is associated with leases of certain airport facilities that were derecognized as part of the build-to-suit transition guidance under the New Lease Standard. The reduction in capitalized interest is also associated with the same airport facilities leases. The table below presents the impact of the adoption of the New Lease Standard on UAL's balance sheet accounts and captions (in millions): December 31, 2018 As Reported New Lease Standard Adjustments As Adjusted Receivables, less allowance for doubtful accounts $ 1,346 $ 80 $ 1,426 Prepaid expenses and other 913 (180 ) 733 Flight equipment, owned and finance leases (a) 32,636 (37 ) 32,599 Other property and equipment, owned and finance leases (a) 7,930 (1,041 ) 6,889 Accumulated depreciation and amortization, owned and finance leases (a) (13,414 ) 148 (13,266 ) Operating lease right-of-use assets — 5,262 5,262 Current maturities of finance leases (a) 149 (26 ) 123 Current maturities of operating leases — 719 719 Other current liabilities 619 (66 ) 553 Long-term obligations under finance leases (a) 1,134 (910 ) 224 Long-term obligations under operating leases — 5,276 5,276 Deferred income taxes 814 14 828 Other long-term liabilities 1,832 (822 ) 1,010 Retained earnings 6,668 47 6,715 (a) Finance leases, under the New Lease Standard, are the equivalent of capital leases under Topic 840. The table below presents the impact of the adoption of the New Lease Standard on select line items of UAL's statement of consolidated cash flows for the year ended December 31 (in millions): As Reported New Lease Standard Adjustments As Adjusted 2018 2017 2018 2017 2018 2017 Cash Flows from Operating Activities: Net cash provided by operating activities $ 6,181 $ 3,413 $ (17 ) $ 61 $ 6,164 $ 3,474 Cash Flows from Investing Activities: Capital expenditures (4,177 ) (3,998 ) 107 128 (4,070 ) (3,870 ) Cash Flows from Financing Activities: Proceeds from issuance of long-term debt 1,740 2,765 (146 ) (228 ) 1,594 2,537 Principal payments under finance leases (134 ) (124 ) 55 40 (79 ) (84 ) The adoption of the New Lease Standard primarily resulted in the recording of assets and liabilities of our operating leases on our consolidated balance sheets. Certain amounts recorded for prepaid and accrued rent associated with historical operating leases were reclassified to the newly captioned Operating lease right-of-use assets in the consolidated balance sheets. Also, certain leases designated under Topic 840 as owned assets and capital leases are not considered to be assets under the New Lease Standard and have been removed from the consolidated balance sheets, along with the related capital lease liability, due to the leases having variable lease payments. In June 2016, the FASB issued Accounting Standards Update No. 2016-13, Financial Instruments-Credit Losses ("ASU 2016-13"). The amendments in this update replace the incurred loss methodology with a methodology that reflects expected credit losses. This update requires financial assets measured at amortized cost basis, such as trade receivables, loans and held-to-maturity debt securities, to be presented at the net amount expected to be collected, and requires entities to record expected losses for certain guarantees and off-balance sheet exposures. The update also eliminates the concept of other-than-temporary impairment for available-for-sale securities. Impairments on available-for-sale securities will be required to be recognized in earnings through an allowance when the fair value is less than amortized cost and a credit loss exists, or the securities are expected to be sold before recovery of amortized cost. The Company adopted ASU 2016-13 on January 1, 2020. The standard update is not expected to have a material impact on the Company's consolidated financial statements.

Common Stockholders' Equity and

Common Stockholders' Equity and Preferred Securities	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Common Stockholders' Equity and Preferred Securities	COMMON STOCKHOLDERS' EQUITY AND PREFERRED SECURITIES In 2019 , UAL repurchased approximately 19.2 million shares of UAL common stock for $1.6 billion . In December 2017, UAL's Board of Directors authorized a $3.0 billion share repurchase program to acquire UAL's common stock. In July 2019, UAL's Board of Directors authorized a new $3.0 billion share repurchase program to acquire UAL's common stock. As of December 31, 2019 , the Company had approximately $3.1 billion remaining to purchase shares under its share repurchase programs. 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. At December 31, 2019 , approximately 8 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, 2019 , UAL had two shares of junior preferred stock (par value $0.01 per share) outstanding. In addition, UAL is authorized to issue 250 million

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Earnings Per Share	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): 2019 2018 (a) 2017 (a) Earnings available to common stockholders $ 3,009 $ 2,122 $ 2,143 Basic weighted-average shares outstanding 258.8 275.5 302.7 Effect of employee stock awards 1.1 1.2 0.9 Diluted weighted-average shares outstanding 259.9 276.7 303.6 Earnings per share, basic $ 11.63 $ 7.70 $ 7.08 Earnings per share, diluted $ 11.58 $ 7.67 $ 7.06 (a) Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 of this report for additional information on the adjustments. 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, 2019
Share-based Payment Arrangement [Abstract]
Share-Based Compensation Plans	SHARE-BASED COMPENSATION PLANS UAL maintains share-based compensation plans for our management employees and our non-employee directors. These plans provide for grants of non-qualified stock options, incentive stock options (within the meaning of Section 422 of the Internal Revenue Code of 1986), stock appreciation rights, restricted shares, RSUs, performance compensation awards, performance units, cash incentive awards, other equity-based and equity-related awards, and dividends and dividend equivalents. 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 2019 , UAL granted share-based compensation awards pursuant to the United Continental Holdings, Inc. 2017 Incentive Compensation Plan. These share-based compensation awards included approximately 1.2 million RSUs consisting of 0.9 million time-vested RSUs and 0.3 million performance-based RSUs and approximately 307,000 stock options. The time-vested RSUs vest pro-rata, a majority of which vest on February 28th of each year, over a three -year period from the date of grant. The amount of performance-based RSUs that vest will be based on the Company's relative improvement in pre-tax margin compared to a group of airline industry peers for the three years ending December 31, 2021 . The RSUs are generally equity awards settled in stock for domestic employees and liability awards settled in cash for international employees. The cash payments are based on the 20 -day average closing price of UAL common stock immediately prior to the vesting date. The stock options have a ten -year term and vest annually over six years , at variable rates, beginning on the third anniversary of UAL's 2020 Annual Meeting of Stockholders. The following table provides information related to UAL's share-based compensation plan cost for the years ended December 31 (in millions): 2019 2018 2017 Compensation cost: RSUs $ 98 $ 98 $ 63 Restricted stock 1 2 8 Stock options 1 1 2 Total $ 100 $ 101 $ 73 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, 2019 (in millions, except as noted): Unearned Compensation Weighted-Average Remaining Period (in years) RSUs $ 66 2.0 Stock options 11 5.3 Total $ 77 RSUs and Restricted Stock. As of December 31, 2019 , UAL had recorded a liability of $44 million related to its cash-settled RSUs. UAL paid $41 million , $28 million and $50 million related to its cash-settled RSUs during 2019 , 2018 and 2017 , respectively. The table below summarizes UAL's RSUs and restricted stock activity for the years ended December 31 (shares in millions): Liability Awards Equity Awards RSUs RSUs Weighted- Average Grant Price Restricted Stock Weighted- Average Grant Price Outstanding at December 31, 2016 2.1 0.8 $ 51.67 0.5 $ 52.00 Granted 0.6 1.0 71.68 — — Vested (0.7 ) (0.3 ) 51.81 (0.2 ) 51.60 Forfeited (0.2 ) (0.1 ) 57.49 — — Outstanding at December 31, 2017 1.8 1.4 63.99 0.3 52.30 Granted 0.7 1.1 67.74 — — Vested (0.5 ) (0.5 ) 63.02 (0.2 ) 53.24 Forfeited (0.1 ) (0.2 ) 67.34 — — Outstanding at December 31, 2018 1.9 1.8 66.29 0.1 51.17 Granted 0.1 1.1 86.72 — — Vested (0.5 ) (0.8 ) 64.85 (0.1 ) 51.17 Forfeited (0.9 ) (0.1 ) 76.48 — — Outstanding at December 31, 2019 0.6 2.0 78.03 — — The fair value of RSUs and restricted stock that vested in 2019 , 2018 and 2017 was $99 million , $70 million and $76 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. 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. Stock Options. In 2019 , UAL granted an award of approximately 307,000 premium-priced stock options with an exercise price that was 25% higher than the closing price of UAL's common stock on the date of grant, representing an exercise price of $110.21 . UAL did not grant any stock option awards during 2018. In 2017, UAL granted approximately 36,000 stock options with an exercise price equal to the fair market value of UAL's common stock on the date of grant, representing an exercise price of $77.56 and a weighted-average grant date fair value of approximately $0.7 million . Expense related to each portion of an option grant is recognized on a straight-line basis over the specific vesting period for those 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 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, 2019 , there were approximately 0.7 million outstanding stock option awards, 0.2 million of which were exercisable, with weighted-average exercise prices of $82.12 and $56.89 , respectively, intrinsic values of $11 million and $6 million , respectively, and weighted-average remaining contractual lives (in years) of 7.3 and 3.7 , respectively.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) ("AOCI") The tables below present the components of the Company's AOCI, net of tax (in millions): Pension and Other Postretirement Liabilities Investments and Other Deferred Taxes Total Balance at December 31, 2016 $ (854 ) $ (1 ) $ 26 $ (829 ) Change in value (306 ) (a) (7 ) 74 (239 ) Amounts reclassified to earnings 58 2 (21 ) 39 Reclassification of stranded tax effects — — (118 ) (b) (118 ) Balance at December 31, 2017 (1,102 ) (6 ) (39 ) (1,147 ) Change in value 377 (a) (5 ) (83 ) 289 Amounts reclassified to earnings 62 — (13 ) 49 Amounts reclassified to retained earnings ("RE") — 7 (c) (1 ) (c) 6 Balance at December 31, 2018 (663 ) (4 ) (136 ) (803 ) Change in value 105 (a) 7 (24 ) 88 Amounts reclassified to earnings (2 ) (1 ) — (3 ) Balance at December 31, 2019 $ (560 ) $ 2 $ (160 ) $ (718 ) (a) This AOCI component is included in the computation of net periodic pension and other postretirement costs. See Note 7 of this report for additional information on pensions and other postretirement liabilities. (b) This amount represents the reclassification from AOCI to RE of the stranded tax effects resulting from the enactment of the Tax Cuts and Jobs Act (the "Tax Act"). (c) These amounts represent the reclassification from AOCI to RE of the unrealized loss, and related tax, on the Company's investment in Azul Linhas Aéreas Brasileiras S.A. ("Azul") which was classified as an available-for-sale security prior to the Company adopting Accounting Standards Update No. 2016-01, Financial Instruments—Overall (Subtopic 825-10) effective January 1, 2018.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	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 (in millions) : UAL 2019 2018 (a) 2017 (a) Income tax provision at statutory rate $ 822 $ 556 $ 1,058 State income taxes, net of federal income tax benefit 50 29 30 Foreign tax rate differential (90 ) (84 ) (43 ) Global intangible low-taxed income 90 4 — Foreign income taxes 1 2 3 Nondeductible employee meals 12 12 17 Impact of Tax Act — (5 ) (189 ) State rate change — 3 12 Valuation allowance (4 ) (3 ) (16 ) Other, net 24 12 8 $ 905 $ 526 $ 880 Current $ 23 $ 14 $ (77 ) Deferred 882 512 957 $ 905 $ 526 $ 880 United 2019 2018 (a) 2017 (a) Income tax provision at statutory rate $ 822 $ 557 $ 1,059 State income taxes, net of federal income tax 50 29 30 Foreign tax rate differential (90 ) (84 ) (43 ) Global intangible low-taxed income 90 4 — Foreign income taxes 1 2 3 Nondeductible employee meals 12 12 17 Impact of Tax Act — (5 ) (206 ) State rate change — 3 12 Valuation allowance (4 ) (3 ) (16 ) Other, net 24 12 8 $ 905 $ 527 $ 864 Current $ 23 $ 14 $ (77 ) Deferred 882 513 941 $ 905 $ 527 $ 864 (a) Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 of this report for additional information on the adjustments. The Company's effective tax rate for the year ended December 31, 2019 differed from the federal statutory rate of 21% due to a blend of federal, state and foreign taxes as well as the impact of certain nondeductible items. On December 22, 2017, Congress enacted the Tax Act, which made significant changes to U.S. federal income tax laws, including reducing the corporate rate from 35% to 21% effective January 1, 2018. The Tax Act included a Global Intangible Low-Taxed Income ("GILTI") provision which introduced a new tax on foreign income in excess of a deemed return on tangible business property of foreign subsidiaries. The GILTI provisions of the Tax Act became effective for the Company during 2018 and we elected to account for it in the period incurred (the "period cost method"). The increase in the GILTI for the year ended December 31, 2019 is due to a full-year inclusion in 2019 as compared to a partial-year inclusion in 2018 . Additionally, the Company did not satisfy the minimum taxable income requirement to benefit from the 50% GILTI deduction provided by the Tax Act. Temporary differences and carryforwards that give rise to deferred tax assets and liabilities at December 31, 2019 and 2018 were as follows (in millions): UAL United 2019 2018 2019 2018 Deferred income tax asset (liability): Federal and state net operating loss ("NOL") carryforwards $ 695 $ 398 $ 668 $ 371 Deferred revenue 1,287 1,232 1,287 1,232 Employee benefits, including pension, postretirement and medical 715 885 715 885 Operating lease liabilities 1,256 1,338 1,256 1,338 Other 165 229 165 229 Less: Valuation allowance (58 ) (59 ) (58 ) (59 ) Total deferred tax assets $ 4,060 $ 4,023 $ 4,033 $ 3,996 Depreciation $ (4,011 ) $ (2,929 ) $ (4,011 ) $ (2,929 ) Operating lease right-of-use asset (1,061 ) (1,173 ) (1,061 ) (1,173 ) Intangibles (724 ) (749 ) (724 ) (749 ) Total deferred tax liabilities $ (5,796 ) $ (4,851 ) $ (5,796 ) $ (4,851 ) Net deferred tax liability $ (1,736 ) $ (828 ) $ (1,763 ) $ (855 ) 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 NOL carryforwards of $3.0 billion for UAL. If not utilized these federal pre-tax NOLs will expire as follows (in billions): $0.7 billion in 2030, $0.5 billion in 2033, and $0.5 billion in 2034. The remaining $1.3 billion of NOLs has no expiration date. In addition, for UAL the majority of tax benefits of the state NOLs of $100 million expire over a five to twenty year period. We have recorded a $45 million valuation allowance against these state NOLs. The Company's unrecognized tax benefits related to uncertain tax positions were $53 million , $39 million and $21 million at December 31, 2019 , 2018 and 2017 , respectively. Included in the ending balance at December 31, 2019 is $53 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 2019 , 2018 and 2017 . 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, 2019 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 2002 remain subject to examination by the Internal Revenue Service (the "IRS") and state taxing jurisdictions. We are currently under audit by the IRS for the 2016 and 2017 tax years.

Pension and Other Postretiremen

Pension and Other Postretirement Plans	12 Months Ended
	Dec. 31, 2019
Retirement Benefits [Abstract]
Pension and Other Postretirement Plans	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 employees. Each of these plans provide benefits based on a combination of years of benefit accruals service and an employee's final average compensation. Additional benefit accruals are frozen under the plan covering certain pilot employees and for management and administrative employees covered under the non-pilot plan. Benefit accruals for certain non-pilot employees continue. United maintains additional defined benefit pension plans, which cover certain international employees. 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, deductibles and other limits as described in the specific plan documentation. During 2019, United notified participants of a refresh to the plan options offered under its retiree medical benefit program. Non-HMO (health maintenance organization) medical plan options for post-Medicare retirees were converted to fully-insured Medicare Advantage plans. The plan design changes impacted all current and future eligible post-Medicare retirees, through updates in plan design and/or premium rate/contribution setting refinements. Benefit levels were not reduced as a result of this change, and in many cases the refresh resulted in reduced retiree contributions. As a result of this modification to its retiree medical plan options, the Company remeasured retiree medical benefit program liabilities using a discount rate of 3.39% . The projected benefit obligation of the retiree medical benefit program decreased by $421 million with an offset to Accumulated other comprehensive loss ( $597 million in prior service credits related to the plan changes, partially offset by $176 million in actuarial losses related to the remeasurement), which will be amortized over the average years of future service to full eligibility for the participants in the retiree medical benefit program (approximately seven years ). Actuarial assumption changes are reflected as a component of the net actuarial (gain)/loss during 2019 and 2018 . The 2019 actuarial losses were mainly related to a decrease in the discount rate applied at December 31, 2019 compared to December 31, 2018 . Actuarial gains/losses will be amortized over the average remaining service life of the covered active employees or the average life expectancy of inactive participants. The following tables set 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 December 31, 2019 Year Ended December 31, 2018 Accumulated benefit obligation: $ 5,333 $ 4,448 Change in projected benefit obligation: Projected benefit obligation at beginning of year $ 5,396 $ 5,852 Service cost 184 228 Interest cost 226 217 Actuarial (gain) loss 784 (601 ) Gross benefits paid and settlements (200 ) (292 ) Other 8 (8 ) Projected benefit obligation at end of year $ 6,398 $ 5,396 Change in plan assets: Fair value of plan assets at beginning of year $ 3,827 $ 3,932 Actual (loss) return on plan assets 684 (215 ) Employer contributions 649 413 Gross benefits paid and settlements (200 ) (292 ) Other 4 (11 ) Fair value of plan assets at end of year $ 4,964 $ 3,827 Funded status—Net amount recognized $ (1,434 ) $ (1,569 ) Pension Benefits December 31, 2019 December 31, 2018 Amounts recognized in the consolidated balance sheets consist of: Noncurrent asset $ 14 $ 13 Current liability (2 ) (6 ) Noncurrent liability (1,446 ) (1,576 ) Total liability $ (1,434 ) $ (1,569 ) Amounts recognized in accumulated other comprehensive loss consist of: Net actuarial loss $ (1,652 ) $ (1,382 ) Prior service cost (4 ) (5 ) Total accumulated other comprehensive loss $ (1,656 ) $ (1,387 ) Other Postretirement Benefits Year Ended December 31, 2019 Year Ended December 31, 2018 Change in benefit obligation: Benefit obligation at beginning of year $ 1,391 $ 1,710 Service cost 10 12 Interest cost 47 61 Plan participants' contributions 67 68 Benefits paid (180 ) (181 ) Actuarial loss (gain) 99 (285 ) Plan amendments (597 ) — Other 5 6 Benefit obligation at end of year $ 842 $ 1,391 Change in plan assets: Fair value of plan assets at beginning of year $ 53 $ 54 Actual return on plan assets 1 1 Employer contributions 111 111 Plan participants' contributions 67 68 Benefits paid (180 ) (181 ) Fair value of plan assets at end of year 52 53 Funded status—Net amount recognized $ (790 ) $ (1,338 ) Other Postretirement Benefits December 31, 2019 December 31, 2018 Amounts recognized in the consolidated balance sheets consist of: Current liability $ (1 ) $ (43 ) Noncurrent liability (789 ) (1,295 ) Total liability $ (790 ) $ (1,338 ) Amounts recognized in accumulated other comprehensive income consist of: Net actuarial gain $ 403 $ 554 Prior service credit 693 170 Total accumulated other comprehensive income $ 1,096 $ 724 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): 2019 2018 Projected benefit obligation $ 6,161 $ 5,196 Accumulated benefit obligation 5,137 4,286 Fair value of plan assets 4,714 3,614 Net periodic benefit cost for the years ended December 31 included the following components (in millions): 2019 2018 2017 Pension Benefits Other Postretirement Benefits Pension Benefits Other Postretirement Benefits Pension Benefits Other Postretirement Benefits Service cost $ 184 $ 10 $ 228 $ 12 $ 195 $ 13 Interest cost 226 47 217 61 220 66 Expected return on plan assets (291 ) (1 ) (292 ) (2 ) (243 ) (2 ) Amortization of unrecognized actuarial (gain) loss 118 (52 ) 130 (32 ) 128 (33 ) Amortization of prior service credits — (73 ) — (37 ) — (37 ) Other 5 — 1 — 5 — Net periodic benefit cost (credit) $ 242 $ (69 ) $ 284 $ 2 $ 305 $ 7 Service cost is recorded in Salaries and related costs on the statement of consolidated operations. All other components of net periodic benefit costs are recorded in Miscellaneous, net on the statement of consolidated operations. The assumptions used for the benefit plans were as follows: Pension Benefits Assumptions used to determine benefit obligations 2019 2018 Discount rate 3.52 % 4.20 % Rate of compensation increase 3.89 % 3.89 % Assumptions used to determine net expense Discount rate 4.21 % 3.65 % Expected return on plan assets 7.40 % 7.31 % Rate of compensation increase 3.89 % 3.89 % A 50 basis points decrease in the weighted average discount rate would have increased the Company's December 31, 2019 pension benefit liability by approximately $0.7 billion and increased the estimated 2019 pension benefit expense by approximately $69 million . Other Postretirement Benefits Assumptions used to determine benefit obligations 2019 2018 Discount rate 3.35 % 4.30 % Assumptions used to determine net expense Discount rate 4.30 % 3.63 % Expected return on plan assets 3.00 % 3.00 % Health care cost trend rate assumed for next year 6.00 % 6.00 % Rate to which the cost trend rate is assumed to decline (ultimate trend rate in 2033) 5.00 % 5.00 % A 50 basis points decrease in the weighted average discount rate would have increased the Company's December 31, 2019 postretirement benefit liability by approximately $42 million and increased the estimated 2019 benefits expense by approximately $4 million . The Company used the Society of Actuaries' PRI-2012 Private Retirement Plans Mortality Tables projected generationally using the Society of Actuaries' MP-2019 projection scale, modified to reflect the Social Security Administration Trustee's Report on current projections regarding expected longevity improvements. The Company selected the 2019 discount rate for substantially all of its plans by using a hypothetical portfolio of high-quality bonds at December 31, 2019 , 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 30-45 % 10 % Fixed-income securities 35-50 5 Alternatives 15-25 7 A 50 basis points decrease in the expected long-term rate of return on plan assets would have increased estimated 2019 pension expense by approximately $20 million . Fair Value Information. Accounting standards require us to use valuation techniques to measure fair value that maximize the use of observable inputs and minimize the use of unobservable inputs. These inputs are prioritized as follows: 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. Prices and other relevant information generated by market transactions involving identical or comparable assets and liabilities; and (b) Income approach. Techniques to convert future amounts to a single current value based on market expectations (including present value techniques, option-pricing and excess earnings models). The following tables present information about United's pension and other postretirement plan assets at December 31, (in millions): 2019 2018 Pension Plan Assets: Total Level 1 Level 2 Level 3 Assets Measured at NAV(a) Total Level 1 Level 2 Level 3 Assets Measured at NAV(a) Equity securities funds $ 1,957 $ 47 $ 117 $ 71 $ 1,722 $ 1,457 $ 254 $ 106 $ 63 $ 1,034 Fixed-income securities 1,732 — 687 69 976 1,520 — 628 87 805 Alternatives 776 — — 205 571 596 — — 134 462 Other investments 499 466 21 12 — 254 224 17 13 — Total $ 4,964 $ 513 $ 825 $ 357 $ 3,269 $ 3,827 $ 478 $ 751 $ 297 $ 2,301 Other Postretirement Benefit Plan Assets: Deposit administration fund $ 52 $ — $ — $ 52 $ — $ 53 $ — $ — $ 53 $ — (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. public- or private-sector entities. Redemption periods for these investments range from daily to semiannually. Equity and Fixed-Income. Equities include investments in both developed market and emerging market equity securities. Fixed-income includes primarily U.S. and non-U.S. government fixed-income securities and U.S. and non-U.S. corporate fixed-income securities. Deposit Administration Fund. This investment is a stable value investment product structured to provide investment income. Alternatives. Alternative investments consist primarily of investments in hedge funds, real estate and private equity interests. Other investments. Other investments consist of primarily cash, as well as insurance contracts. The reconciliation of United's benefit plan assets measured at fair value using unobservable inputs (Level 3) for the years ended December 31, 2019 and 2018 is as follows (in millions): 2019 2018 Balance at beginning of year $ 350 $ 383 Actual return (loss) on plan assets: Sold during the year 12 10 Held at year end (1 ) (21 ) Purchases, sales, issuances and settlements (net) 48 (22 ) Balance at end of year $ 409 $ 350 Funding requirements for tax-qualified defined benefit pension plans are determined by government regulations. United's contributions reflected above have satisfied its required contributions through the 2019 calendar year. In 2020 , employer anticipated contributions to all of United's pension and postretirement plans are at least $314 million and approximately $47 million , respectively. The estimated future benefit payments, net of expected participant contributions, in United's pension plans and other postretirement benefit plans as of December 31, 2019 are as follows (in millions): Pension Other Postretirement 2020 $ 361 $ 53 2021 386 56 2022 399 59 2023 410 62 2024 399 64 Years 2025 – 2029 2,219 328 Defined Contribution Plans. Depending upon the employee group, employer contributions consist of matching contributions and/or non-elective employer contributions. United's employer contribution percentages vary from 1% to 16% of eligible earnings depending on the terms of each plan. United recorded expenses for its defined contribution plans of $735 million , $693 million and $656 million in the years ended December 31, 2019 , 2018 and 2017 , respectively. Multi-Employer Plans. United's participation in the IAM National Pension Plan ("IAM Plan") for the annual period ended December 31, 2019 is outlined in the table below. Except as described in table below, there have been no other changes that affect the comparability of 2019 and 2018 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 $467 million in employers' contributions for the year ended December 31, 2018 . For 2018 , the Company's contributions to the IAM Plan represented more than 5% of total contributions to the IAM Plan. The 2019 information is not available as Form 5500 is not final for the plan year. Pension Fund IAM National Pension Fund EIN/ Pension Plan Number 51-6031295 - 002 Pension Protection Act Zone Status (2019 and 2018) Red Zone (2019) and Green Zone (2018). Plans in the Green Zone are at least 80 percent funded. Plans in the Red Zone are less than 65% funded. The IAM National Pension Fund Board of Trustees voluntarily elected to place the fund in the Red Zone for 2019, although the fund was over 80% funded at the time, to protect the fund's participants' core retirement benefits and strengthen the fund's financial health over the long term. FIP/RP Status Pending/Implemented A 10-year Rehabilitation Plan effective, January 1, 2022, was adopted on April 17, 2019 that requires the Company to make an additional contribution of 2.5% of the hourly contribution rate, compounded annually for the length of the Rehabilitation Plan, effective June 1, 2019. United's Contributions $59 million, $52 million and $50 million in the years ended December 31, 2019, 2018 and 2017, respectively Surcharge Imposed No Expiration Date of Collective Bargaining Agreement N/A Profit Sharing. Substantially all employees participate in profit sharing based on a percentage of pre-tax earnings, excluding special charges, profit sharing expense and share-based compensation. Profit sharing percentages range from 5% to 20% depending on the work group, and in some cases profit sharing percentages vary above and below certain pre-tax margin thresholds. Eligible U.S. co-workers in each participating work group receive a profit sharing payout using a formula based on the ratio of each qualified co-worker's annual eligible earnings to the eligible earnings of all qualified co-workers in all domestic work groups. Eligible non-U.S. co-workers receive profit sharing based on the calculation under the U.S. profit sharing plan for management and administrative employees. The Company recorded profit sharing and related payroll tax expense of $491 million , $334 million and $349 million in 2019 , 2018 and 2017 , respectively. Profit sharing expense is recorded as a component of Salaries and related costs in the Company's statements of consolidated operations.

Notes Receivable

Notes Receivable	12 Months Ended
	Dec. 31, 2019
Receivables [Abstract]
Notes Receivables	NOTES RECEIVABLE BRW Term Loan. In November 2018, United, as lender, entered into a Term Loan Agreement (the "BRW Term Loan Agreement") with, among others, BRW Aviation Holding LLC and BRW Aviation LLC ("BRW"), as guarantor and borrower, respectively, BRW Aviation Holding LLC and BRW are affiliates of Synergy Aerospace Corporation ("Synergy"), and BRW is the majority shareholder of Avianca Holdings S.A. ("AVH"). Pursuant to the BRW Term Loan Agreement, United provided to BRW a $456 million term loan (the "BRW Term Loan"), secured by a pledge of BRW's equity, as well as BRW's 516 million common shares of AVH (which are eligible to be converted into the same number of preferred shares, which may be deposited with the depositary for AVH's American Depositary Receipts ("ADRs"), the class of AVH securities that trades on the New York Stock Exchange (the "NYSE"), in exchange for 64.5 million ADRs) (such equity and shares, collectively, the "BRW Loan Collateral"). BRW is currently in default under the BRW Term Loan Agreement. In order to protect the value of its collateral, on May 24, 2019, United began to exercise certain remedies available to it under the terms of the BRW Term Loan Agreement and related documents. In connection with the delivery by United of a notice of default to BRW, Kingsland Holdings Limited ("Kingsland"), AVH's largest minority shareholder, was granted, in accordance with the agreements related to the BRW Term Loan Agreement, authority to manage BRW, which remains the majority shareholder of AVH. In addition, Kingsland is pursuing a foreclosure process which is expected to result in a judicially supervised sale of the BRW Loan Collateral. United evaluated the $499 million carrying value of the BRW Term Loan as of December 31, 2019 using the fair value of the BRW Loan Collateral and determined that the value of the BRW Loan Collateral is sufficient to recover the carrying value of the BRW Term Loan. As a result, the Company concluded that the BRW Term Loan is not impaired. The carrying value of the BRW Term Loan represents the original loan amount plus accrued and unpaid interest and certain expenses associated with the loan origination. The fair market value of AVH equity was estimated using an income approach and a market approach with equal weight applied to each approach. Under the income approach, the value was estimated by discounting expected future cash flows at a weighted average cost of capital to a single present value amount. Under the market approach, the value was estimated by reference to multiples of enterprise value to earnings before interest, taxes, depreciation, amortization and rent ("EBITDAR") for a group of publicly-traded market comparable companies, along with AVH's own EBITDAR levels. Avianca Loan. In November 2019, United entered into a senior secured convertible term loan agreement (the "AVH Convertible Loan Agreement") with, among others, AVH, as borrower, for the provision by the lenders thereunder (including United) to AVH of convertible term loans for general corporate purposes. In December 2019, United provided such a convertible term loan to AVH under the AVH Convertible Loan Agreement in the aggregate amount of $150 million (the "AVH Convertible Loan"). The AVH Convertible Loan (1) is payable in a single installment in December 2023, (2) bears paid-in-kind interest at a rate of 3 percent per annum ("PIK Interest") and (3) is secured by a pledge of capital stock in AVH's major subsidiaries and, until released, certain Colombian Peso-denominated credit card receivables owing to Aerovias del Continente Americano S.A. ("Avianca"), a subsidiary of AVH and guarantor under the AVH Convertible Loan Agreement. United has the option to convert the AVH Convertible Loan, in minimum $5 million principal increments, into equity of AVH at a conversion price of $4.6217 per one American Depositary Share (as evidenced by an ADR) or eight AVH shares. Following the occurrence of a change of control of AVH, the conversion price will be reduced to $4.1595 per ADR. Additionally, AVH may, on or after the day occurring 360 days after the funding date of the AVH Convertible Loan, require that United convert 100% of the outstanding principal amount (including capitalized PIK Interest) of the AVH Convertible Loan, together with accrued cash interest thereon, into AVH shares, if certain conditions are satisfied, including conditions corresponding to a minimum volume-weighted average market price of AVH ADRs and a minimum AVH average cash balance. As of December 31, 2019 , the fair value of the AVH Convertible Loan approximated its carrying value.

Investments and Fair Value Meas

Investments and Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Investments and Fair Value Measurements	INVESTMENTS AND FAIR VALUE MEASUREMENTS Fair Value Information. Accounting standards require us to use valuation techniques to measure fair value that maximize the use of observable inputs and minimize the use of unobservable inputs. These inputs are described in Note 7 of this report. 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): 2019 2018 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Cash and cash equivalents $ 2,762 $ 2,762 $ — $ — $ 1,694 $ 1,694 $ — $ — Short-term investments: Corporate debt 1,045 — 1,045 — 1,023 — 1,023 — Asset-backed securities 690 — 690 — 746 — 746 — U.S. government and agency notes 124 — 124 — 108 — 108 — Certificates of deposit placed through an account registry service ("CDARS") 35 — 35 — 75 — 75 — Other fixed-income securities 95 — 95 — 116 — 116 — Other investments measured at NAV 193 — — — 188 — — — Restricted cash 106 106 — — 105 105 — — Long-term investments: Equity securities 385 385 — — 249 249 — — AVH Derivative Assets 24 — — 24 11 — — 11 Available-for-sale investment maturities - T he short-term investments shown in the table above are classified as available-for-sale, with the exception of investments measured at NAV. As of December 31, 2019 , asset-backed securities have remaining maturities of less than one year to approximately 15 years , corporate debt securities have remaining maturities of three years or less and CDARS have maturities of less than one year . U.S. government and agency notes have maturities of approximately three years or less and other fixed-income securities have maturities of two years or less. Restricted cash - Restricted cash primarily includes cash collateral for letters of credit and collateral associated with obligations for facility leases and other insurance-related obligations. Equity securities - Equity securities represent United's investment in Azul, consisting of approximately 8% of Azul's outstanding preferred shares (representing approximately 2% of the total capital stock of Azul). The Company recognizes changes to the fair value of its equity investment in Azul in Unrealized gains (losses) on investments, net in its statements of consolidated operations. The carrying value of our investment in Azul was $385 million at December 31, 2019 . AVH Derivative Assets - As part of the BRW Term Loan Agreement and related agreements with Kingsland, United obtained call options on AVH shares, AVH share appreciation rights and an AVH share-based upside sharing agreement (collectively, the "AVH Derivative Assets"). The AVH Derivative Assets are recorded at fair value as Other assets on the Company's balance sheet and are included in the table above. Changes in the fair value of the AVH Derivative Assets are recorded as part of Unrealized gains (losses) on investments, net in its statements of consolidated operations. Investments presented in the table above have the same fair value as their carrying value. Other fair value information - 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). Carrying amounts include any related discounts, premiums and issuance costs: 2019 2018 Carrying Amount Fair Value Carrying Amount Fair Value Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Long-term debt $ 14,552 $ 15,203 $ — $ 11,398 $ 3,805 $ 13,445 $ 13,450 $ — $ 9,525 $ 3,925 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 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. public- or private-sector entities. The Company can redeem its shares at any time at NAV subject to a three-day settlement period. AVH Derivative Assets Fair values are calculated using a Monte Carlo simulation approach. Unobservable inputs include expected volatility, expected dividend yield and control and acquisition premiums. 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 or assets. Investments in Regional Carriers . United holds investments in several regional carriers that fly for the Company as United Express under its capacity purchase agreements ("CPAs"). The combined carrying value of the investments was approximately $126 million as of December 31, 2019 . United accounts for each investment using the equity method. Each investment and United's ownership stake are listed below. • Republic Airways Holdings Inc. ("Republic"). United holds a 19% minority interest in Republic which the Company received in 2017 in consideration for its unsecured claim in Republic's bankruptcy case. Republic is the parent company of Republic Airline Inc. • ManaAir, LLC ("ManaAir"). United holds a 49.9% minority ownership stake in ManaAir. ManaAir is the parent company of ExpressJet Airlines LLC. • Champlain Enterprises, LLC ("Champlain"). United owns a 40% minority ownership stake in Champlain. Champlain does business as CommutAir. Other Investments. United owns approximately 8% of the preferred shares (representing approximately 7% of the total capital stock) of Fulcrum BioEnergy, Inc. ("Fulcrum"), a company that is developing a process for transforming municipal solid waste into transportation fuels, including jet fuel and diesel. United records its investment in Fulcrum at cost less impairment, adjusted for observable price changes in orderly transactions for an identical or similar investment of the same issuer. As of December 31, 2019 , the carrying value of United's investment was $51 million .

Debt

Debt	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Debt	DEBT (In millions) At December 31, 2019 2018 Secured Notes payable, fixed interest rates of 2.7% to 9.8% (weighted average rate of 3.95% as of December 31, 2019), payable through 2032 $ 9,615 $ 8,811 Notes payable, floating interest rates of the London interbank offered rate ("LIBOR") plus 1.05% to 2.25%, payable through 2030 1,970 2,051 Term loan, LIBOR plus 1.75%, or alternative rate based on certain market rates plus 0.75%, due 2024 1,459 1,474 Unsecured 6% Senior Notes due 2020 (a) 300 300 4.25% Senior Notes due 2022 (a) 400 400 5% Senior Notes due 2024 (a) 300 300 4.875% Senior Notes due 2025 (a) 350 — Other 339 300 14,733 13,636 Less: unamortized debt discount, premiums and debt issuance costs (181 ) (191 ) Less: current portion of long-term debt (1,407 ) (1,230 ) Long-term debt, net $ 13,145 $ 12,215 (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, 2019 under then-outstanding long-term debt agreements in each of the next five calendar years (in millions): 2020 $ 1,407 2021 1,415 2022 1,765 2023 815 2024 3,122 After 2024 6,209 $ 14,733 Secured debt Credit and Guaranty Agreement. United and UAL, as borrower and guarantor, respectively, are parties to the Amended and Restated Credit and Guaranty Agreement (as amended, the "Credit Agreement"). The Credit Agreement consists of a $1.5 billion term loan due April 1, 2024 and a $2.0 billion revolving credit facility available for drawing until its maturity date on April 1, 2022. The obligations of United under the amended Credit Agreement are secured by liens on certain international route authorities, certain take-off and landing rights and related assets of United. Term loan borrowings under the Credit Agreement bear interest at a variable rate equal to LIBOR plus a margin of 1.75% per annum, or another rate based on certain market interest rates, plus a margin of 0.75% 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. As of December 31, 2019 , United had its entire capacity of $2.0 billion available under the revolving credit facility of the Company's Credit Agreement. United pays a commitment fee equal to 0.75% per annum on the undrawn amount available under the revolving credit facility. If drawn, revolving loans under the Credit Agreement bear interest at a variable rate equal to LIBOR plus a margin of 2.25% per annum, or another rate based on certain market interest rates, plus a margin of 1.25% per annum. EETCs. As of December 31, 2019, United had $9.6 billion principal amount of equipment notes outstanding issued under enhanced equipment trust certificates ("EETC") financings included in notes payable in the table of outstanding debt above. Generally, the structure of these EETC financings consists of pass-through trusts created by United to issue pass-through certificates, which represent fractional undivided interests in the respective pass-through trusts and are not obligations of United. The proceeds of the issuance of the pass-through certificates are used to purchase equipment notes which are issued by United and secured by its aircraft. The payment obligations under the equipment notes are those of United. Proceeds received from the sale of pass-through certificates are initially held by a depositary in escrow for the benefit of the certificate holders until United issues equipment notes to the trust, which purchases such notes with a portion of the escrowed funds. These escrowed funds are not guaranteed by United and are not reported as debt on United's consolidated balance sheet because the proceeds held by the depositary are not United's assets. In February and September 2019, United created new 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 2019 are as follows (in millions, except stated interest rate): EETC Issuance Date Class Principal Final expected distribution date Stated interest rate Total proceeds received from issuance of debt during 2019 and recorded as debt as of December 31, 2019 Amounts returned to the holders of the Pass-Through Certificates (a) Remaining proceeds from issuance of debt to be received in future periods September 2019 AA $ 702 May 2032 2.70% $ 513 $ — $ 189 September 2019 A 287 May 2028 2.90% 210 — 77 September 2019 B 232 May 2028 3.50% 170 — 62 February 2019 AA 717 August 2031 4.15% 651 66 — February 2019 A 296 August 2031 4.55% 269 27 — $ 2,234 $ 1,813 $ 93 $ 328 (a) These proceeds were expected to be used to purchase equipment notes issued by United and secured by three Boeing 737 MAX aircraft, which aircraft were scheduled for delivery by Boeing in 2019. However, as a result of the Federal Aviation Administration Order prohibiting the operation of Boeing 737 MAX series aircraft by U.S. certificated operators (the "FAA Order"), United did not take delivery of these aircraft. These amounts were distributed to the holders of February 2019 Pass Through Certificates together with accrued and unpaid interest thereon but without premium. As a result of the FAA Order, the Company did not contemplate using any proceeds from the September 2019 issuance of the EETC pass-through trusts to fund any Boeing 737 MAX deliveries. In 2019 , United borrowed approximately $105 million aggregate principal amount from various financial institutions to finance the purchase of several aircraft delivered in 2019 . The notes evidencing these borrowings, which are secured by the related aircraft, mature in 2029 and have interest rates comprised of LIBOR plus a specified margin. In November 2019 , at the request of United, the California Municipal Finance Authority issued its approximately $295 million special facility revenue bonds and loaned the proceeds of such bonds to United pursuant to a loan agreement to finance the costs of construction of an aircraft maintenance and ground service equipment complex at Los Angeles International Airport. The bonds bear interest at 4% per annum, payable semiannually, commencing July 15, 2020 through the July 15, 2029 maturity date. As security for United's obligations under the loan agreement, United also entered into a leasehold mortgage which grants to the trustee of the bonds (acting on behalf of the bondholders) a lien on United's interest in the leased premises and any improvements thereon owned by or leased to United. As of December 31, 2019, United had recorded approximately $39 million related to this debt. Unsecured debt 4.875% Senior Notes due 2025. In May 2019, UAL issued $350 million aggregate principal amount of 4.875% Senior Notes due January 15, 2025 (the " 4.875% Senior Notes due 2025"), which are fully and unconditionally guaranteed and recorded by United on its balance sheet. As of December 31, 2019 , 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 and landing slots at certain airports and certain other assets. 6% Senior Notes due 2020 4.25% Senior Notes due 2022 5% Senior Notes due 2024 4.875% Senior Notes due 2025 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 programs.

Leases and Capacity Purchase Ag

Leases and Capacity Purchase Agreements	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Leases and Capacity Purchase Agreements	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, among other items. Certain of these leases include provisions for variable lease payments which are based on several factors, including, but not limited to, relative leased square footage, available seat miles, enplaned passengers, passenger facility charges, terminal equipment usage fees, departures, and airports' annual operating budgets. Due to the variable nature of the rates, these leases are not recorded on our balance sheet as a right-of-use asset and lease liability. For leases with terms greater than 12 months, we record the related right-of-use asset and lease liability at the present value of fixed lease payments over the lease term. To the extent a lease agreement includes an extension option that is reasonably certain to be exercised, we have recognized those amounts as part of our right-of-use assets and lease liabilities. Leases with an initial term of 12 months or less with purchase options or extension options that are not reasonably certain to be exercised are not recorded on the balance sheet; we recognize lease expense for these leases on a straight-line basis over the term of the lease. We combine lease and non-lease components, such as common area maintenance costs, in calculating the right-of-use assets and lease liabilities for all asset groups except for our CPAs, which contain embedded leases for regional aircraft. In addition to the lease component cost for regional aircraft, our CPAs also include non-lease components primarily related to the regional carriers' operating costs incurred in providing regional aircraft services. We allocate consideration for the lease components and non-lease components of each CPA based on their relative standalone values. Lease Cost . The Company's lease cost for the years ended December 31 included the following components (in millions): 2019 2018 2017 Operating lease cost $ 1,038 $ 1,213 $ 1,433 Variable and short-term lease cost 2,548 2,569 2,209 Amortization of finance lease assets 68 75 77 Interest on finance lease liabilities 85 44 24 Sublease income (32 ) (38 ) (36 ) Total lease cost $ 3,707 $ 3,863 $ 3,707 Lease terms and commitments . United's leases include aircraft leases for aircraft that are directly leased by United and aircraft that are operated by regional carriers on United's behalf under CPAs (but excluding aircraft owned by United) and non-aircraft leases. Aircraft operating leases relate to leases of 114 mainline and 325 regional aircraft while finance leases relate to leases of 28 mainline and 17 regional aircraft. United's aircraft leases have remaining lease terms of one month to 10 years with expiration dates ranging from 2020 through 2029 . Under the terms of most aircraft 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 a percentage of cost. Non-aircraft leases have remaining lease terms of one month to 34 years , with expiration dates ranging from 2020 through 2053 . The table below summarizes the Company's scheduled future minimum lease payments under operating and finance leases, recorded on the balance sheet, as of December 31, 2019 (in millions): Operating Leases Finance Leases 2020 $ 920 $ 62 2021 754 75 2022 591 49 2023 633 38 2024 626 35 After 2024 4,214 57 Minimum lease payments 7,738 316 Imputed interest (2,106 ) (50 ) Present value of minimum lease payments 5,632 266 Less: current maturities of lease obligations (686 ) (46 ) Long-term lease obligations $ 4,946 $ 220 As of December 31, 2019 , we have additional leases of approximately $500 million for several mainline aircraft, regional jets under a CPA and airport facilities and office space leases that have not yet commenced. These leases will commence in 2020 and 2021 with lease terms of up to 13 years . Our lease agreements do not provide a readily determinable implicit rate nor is it available to us from our lessors. Instead, we estimate United's incremental borrowing rate based on information available at lease commencement in order to discount lease payments to present value. The table below presents additional information related to our leases as of December 31: 2019 2018 Weighted-average remaining lease term - operating leases 11 years 10 years Weighted-average remaining lease term - finance leases 6 years 5 years Weighted-average discount rate - operating leases 5.2 % 5.2 % Weighted-average discount rate - finance leases 5.7 % 45.8 % The table below presents supplemental cash flow information related to leases during the year ended December 31 (in millions): 2019 2018 2017 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 902 $ 1,078 $ 1,451 Operating cash flows for finance leases 70 53 24 Financing cash flows for finance leases 151 79 84 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 rate adjustment based on agreed performance metrics, subject to annual adjustments. The fees are based on specific rates multiplied by specific operating statistics (e.g., block hours, departures), as well as fixed monthly amounts. Under these CPAs, the Company is also 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. In some cases, the Company owns some or all of the aircraft subject to the CPA and leases such aircraft to the regional carrier. United's CPAs are for 581 regional aircraft as of December 31, 2019 , 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 and operated by the regional carriers. See Part I, Item 2. Properties, of this report for additional information. In 2019, United amended an agreement with GoJet Airlines to operate up to 54 Bombardier CRJ-550s under a 10 -year CPA arrangement. United also amended an agreement with Mesa Airlines, which added 20 new Embraer E175 LL aircraft under a 12 -year CPA and also extended 42 United-owned Embraer E175 aircraft for an additional 5 years . United recorded approximately $1 billion , $979 million and $907 million in expenses related to its CPAs with its regional carriers in which United is a minority shareholder, for the years ended December 31, 2019 , 2018 and 2017 , respectively. There were approximately $69 million and $53 million in accounts payable due to these companies as of December 31, 2019 and December 31, 2018 , respectively. There were no material accounts receivables due from these companies as of December 31, 2019 and December 31, 2018 . The CPAs with these related parties were executed in the ordinary course of business. 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 operating leases above. 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, 2019 , our future payments through the end of the terms of our CPAs are presented in the table below (in billions): 2020 $ 2.9 2021 2.9 2022 2.4 2023 1.5 2024 1.3 After 2024 4.7 $ 15.7 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 2020 would result in a corresponding change in annual cash obligations under the CPAs of approximately $202 million .
Leases and Capacity Purchase Agreements	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, among other items. Certain of these leases include provisions for variable lease payments which are based on several factors, including, but not limited to, relative leased square footage, available seat miles, enplaned passengers, passenger facility charges, terminal equipment usage fees, departures, and airports' annual operating budgets. Due to the variable nature of the rates, these leases are not recorded on our balance sheet as a right-of-use asset and lease liability. For leases with terms greater than 12 months, we record the related right-of-use asset and lease liability at the present value of fixed lease payments over the lease term. To the extent a lease agreement includes an extension option that is reasonably certain to be exercised, we have recognized those amounts as part of our right-of-use assets and lease liabilities. Leases with an initial term of 12 months or less with purchase options or extension options that are not reasonably certain to be exercised are not recorded on the balance sheet; we recognize lease expense for these leases on a straight-line basis over the term of the lease. We combine lease and non-lease components, such as common area maintenance costs, in calculating the right-of-use assets and lease liabilities for all asset groups except for our CPAs, which contain embedded leases for regional aircraft. In addition to the lease component cost for regional aircraft, our CPAs also include non-lease components primarily related to the regional carriers' operating costs incurred in providing regional aircraft services. We allocate consideration for the lease components and non-lease components of each CPA based on their relative standalone values. Lease Cost . The Company's lease cost for the years ended December 31 included the following components (in millions): 2019 2018 2017 Operating lease cost $ 1,038 $ 1,213 $ 1,433 Variable and short-term lease cost 2,548 2,569 2,209 Amortization of finance lease assets 68 75 77 Interest on finance lease liabilities 85 44 24 Sublease income (32 ) (38 ) (36 ) Total lease cost $ 3,707 $ 3,863 $ 3,707 Lease terms and commitments . United's leases include aircraft leases for aircraft that are directly leased by United and aircraft that are operated by regional carriers on United's behalf under CPAs (but excluding aircraft owned by United) and non-aircraft leases. Aircraft operating leases relate to leases of 114 mainline and 325 regional aircraft while finance leases relate to leases of 28 mainline and 17 regional aircraft. United's aircraft leases have remaining lease terms of one month to 10 years with expiration dates ranging from 2020 through 2029 . Under the terms of most aircraft 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 a percentage of cost. Non-aircraft leases have remaining lease terms of one month to 34 years , with expiration dates ranging from 2020 through 2053 . The table below summarizes the Company's scheduled future minimum lease payments under operating and finance leases, recorded on the balance sheet, as of December 31, 2019 (in millions): Operating Leases Finance Leases 2020 $ 920 $ 62 2021 754 75 2022 591 49 2023 633 38 2024 626 35 After 2024 4,214 57 Minimum lease payments 7,738 316 Imputed interest (2,106 ) (50 ) Present value of minimum lease payments 5,632 266 Less: current maturities of lease obligations (686 ) (46 ) Long-term lease obligations $ 4,946 $ 220 As of December 31, 2019 , we have additional leases of approximately $500 million for several mainline aircraft, regional jets under a CPA and airport facilities and office space leases that have not yet commenced. These leases will commence in 2020 and 2021 with lease terms of up to 13 years . Our lease agreements do not provide a readily determinable implicit rate nor is it available to us from our lessors. Instead, we estimate United's incremental borrowing rate based on information available at lease commencement in order to discount lease payments to present value. The table below presents additional information related to our leases as of December 31: 2019 2018 Weighted-average remaining lease term - operating leases 11 years 10 years Weighted-average remaining lease term - finance leases 6 years 5 years Weighted-average discount rate - operating leases 5.2 % 5.2 % Weighted-average discount rate - finance leases 5.7 % 45.8 % The table below presents supplemental cash flow information related to leases during the year ended December 31 (in millions): 2019 2018 2017 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 902 $ 1,078 $ 1,451 Operating cash flows for finance leases 70 53 24 Financing cash flows for finance leases 151 79 84 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 rate adjustment based on agreed performance metrics, subject to annual adjustments. The fees are based on specific rates multiplied by specific operating statistics (e.g., block hours, departures), as well as fixed monthly amounts. Under these CPAs, the Company is also 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. In some cases, the Company owns some or all of the aircraft subject to the CPA and leases such aircraft to the regional carrier. United's CPAs are for 581 regional aircraft as of December 31, 2019 , 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 and operated by the regional carriers. See Part I, Item 2. Properties, of this report for additional information. In 2019, United amended an agreement with GoJet Airlines to operate up to 54 Bombardier CRJ-550s under a 10 -year CPA arrangement. United also amended an agreement with Mesa Airlines, which added 20 new Embraer E175 LL aircraft under a 12 -year CPA and also extended 42 United-owned Embraer E175 aircraft for an additional 5 years . United recorded approximately $1 billion , $979 million and $907 million in expenses related to its CPAs with its regional carriers in which United is a minority shareholder, for the years ended December 31, 2019 , 2018 and 2017 , respectively. There were approximately $69 million and $53 million in accounts payable due to these companies as of December 31, 2019 and December 31, 2018 , respectively. There were no material accounts receivables due from these companies as of December 31, 2019 and December 31, 2018 . The CPAs with these related parties were executed in the ordinary course of business. 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 operating leases above. 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, 2019 , our future payments through the end of the terms of our CPAs are presented in the table below (in billions): 2020 $ 2.9 2021 2.9 2022 2.4 2023 1.5 2024 1.3 After 2024 4.7 $ 15.7 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 2020 would result in a corresponding change in annual cash obligations under the CPAs of approximately $202 million .

Variable Interest Entities ("VI

Variable Interest Entities ("VIE")	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable Interest Entities (VIE)	VARIABLE INTEREST ENTITIES ("VIE") 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. 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. Aircraft Leases . We are the lessee in a number of operating leases covering the majority of our leased aircraft. The lessors are trusts established specifically to purchase, finance and lease aircraft to us. These leasing entities meet the criteria for VIEs. We are generally not the primary beneficiary of the leasing entities if the lease terms are consistent with market terms at the inception of the lease and do not include a residual value guarantee, fixed-price purchase option or similar feature that obligates us to absorb decreases in value or entitles us to participate in increases in the value of the aircraft. This is the case for many of our operating leases; however, leases of six mainline jet aircraft contain a fixed-price purchase option that allow United to purchase the aircraft at predetermined prices on specified dates during the lease term. Additionally, leases covering 60 leased regional jet aircraft contain an option to purchase the aircraft at the end of the lease term at prices that, depending on market conditions, could be below fair value. United has not consolidated the related trusts because, even taking into consideration these purchase options, United is still not the primary beneficiary. United's maximum exposure under these leases is the remaining lease payments, which are reflected in future lease commitments in Note 11 of this report. Airport Leases . 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 $1.9 billion of tax-exempt special facilities revenue bonds and interest thereon as of December 31, 2019. These leases are typically with municipalities or other governmental entities, which are excluded from the consolidation requirements concerning a 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. See Note 13 of this report for more information regarding United's guarantee of the tax-exempt special facilities revenue bonds. EETCs. United evaluated whether the pass-through trusts formed for its EETC financings, treated as either debt or aircraft operating leases, are VIEs required to be consolidated by United under applicable accounting guidance, and determined that the pass-through trusts are VIEs. Based on United's analysis as described below, United determined that it does not have a variable interest in the pass-through trusts. 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 ratios for more senior debt classes. These credit enhancements lower United's total borrowing cost. Pass-through trusts are established to receive principal and interest payments on the equipment notes purchased by the pass-through trusts from United and remit these proceeds to the pass-through trusts' certificate holders. 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 does not intend to have any voting or non-voting equity interest in the pass-through trusts or to absorb variability from the pass-through trusts. Based on this analysis, the Company determined that it is not required to consolidate the pass-through trusts. BRW. Synergy's wholly-owned affiliate, BRW, is a special purpose entity created to be the borrower of the BRW Term Loan. BRW is also the owner of the collateral that secures the BRW Term Loan. BRW is a VIE and United holds variable interests in BRW including the BRW Term Loan. However, United is not the primary beneficiary of BRW because it does not hold BRW equity and does not have management rights at BRW and therefore does not have the power to direct the activities that most significantly impact BRW's economic performance. In connection with the delivery by United of a notice of default to BRW, Kingsland was granted, in accordance with the agreements related to the BRW Term Loan Agreement, authority to manage BRW. AVH. United concluded that AVH is a VIE and that United holds a variable interest through the AVH Convertible Loan and a call option on BRW's AVH shares. However, United is not the primary beneficiary because it does not hold a material number of shares of AVH and does not have the power through the AVH Convertible Loan Agreement or any other agreement to direct the activities that most significantly impact AVH's economic performance. See Note 8 of this report for more information regarding the AVH Convertible Loan and Note 9 of this report for more information about the AVH call options.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Commitments. As of December 31, 2019 , United had firm commitments and options to purchase aircraft from The Boeing Company ("Boeing"), Airbus S.A.S. ("Airbus") and Embraer S.A. ("Embraer") presented in the table below: Scheduled Aircraft Deliveries Aircraft Type Number of Firm 2020 After 2020 Airbus A321XLR 50 — 50 Airbus A350 45 — 45 Boeing 737 MAX 171 44 127 Boeing 777-300ER 2 2 — Boeing 787 16 15 1 Embraer E175 20 20 — (a) United also has options and purchase rights for additional aircraft. The aircraft listed in the table above are scheduled for delivery through 2030 . The Company expects to assign the purchase obligation for each of the 20 Embraer E175 aircraft to one of its regional partners at the time of such aircraft's delivery, subject to certain conditions. To the extent the Company and the aircraft manufacturers with which the Company has existing orders for new aircraft agree to modify the contracts governing those orders, the amount and timing of the Company's future capital commitments could change. United also has agreements to purchase 20 used Airbus A319 aircraft with expected delivery dates through 2022 and 19 used Boeing 737-700 aircraft with expected delivery dates through 2021 . The 44 Boeing 737 MAX aircraft in the table above include 16 Boeing B737 MAX aircraft of which the Company planned to take delivery in 2019, and 28 aircraft of which the Company planned to take delivery in 2020; however, following the FAA Order, Boeing suspended deliveries of new Boeing 737 MAX aircraft. The extent of the delay to the scheduled deliveries of new 737 MAX aircraft is expected to be impacted by the length of time the FAA Order remains in place, Boeing's production rate and the pace at which Boeing can deliver aircraft following the lifting of the FAA Order, among other factors. As a result, the Company is unable to estimate the number of Boeing 737 MAX aircraft of which it will take delivery in 2020. The table below summarizes United's commitments as of December 31, 2019 , which include aircraft and related spare engines, aircraft improvements and all non-aircraft capital commitments (in billions): 2020 $ 6.9 2021 4.3 2022 2.0 2023 1.0 2024 1.2 After 2024 11.3 $ 26.7 The Company secured $328 million of EETC financing to finance certain aircraft deliveries in 2020. 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. The Company has certain contingencies resulting from litigation and claims incident to the ordinary course of business. As of December 31, 2019 , management believes, after considering a number of factors, including (but not limited to) the information currently available, the views of legal counsel, the nature of contingencies to which the Company is subject and prior experience, that the ultimate disposition of the litigation and claims will not materially affect the Company's consolidated financial position or results of operations. The Company records liabilities for legal and environmental claims when a loss is probable and reasonably estimable. These amounts are recorded based on the Company's assessments of the likelihood of their eventual disposition. Guarantees and Indemnifications. In the normal course of business, the Company enters into numerous real estate leasing and aircraft financing arrangements that have various guarantees included in the contracts. These guarantees are primarily in the form of indemnities under which the Company typically indemnifies the lessors and any tax/financing parties against liabilities that arise out of or relate to the use, operation or maintenance of the leased premises or financed aircraft. Currently, the Company believes that any future payments required under these guarantees or indemnities would be immaterial, as most liabilities and related indemnities are covered by insurance (subject to deductibles). Additionally, certain real estate leases include indemnities for any environmental liability that may arise out of or relate to the use of the leased premises. As of December 31, 2019 , United is the guarantor of approximately $1.9 billion in aggregate principal amount of tax-exempt special facilities revenue bonds and interest thereon. These bonds, issued by various airport municipalities, are payable solely from rentals paid under long-term agreements with the respective governing bodies. The leasing arrangements associated with these obligations are accounted for as operating leases recognized on the Company's balance sheet with the associated expense recorded on a straight-line basis over the expected lease term. The obligations associated with these tax-exempt special facilities revenue bonds are included in our lease commitments disclosed in Note 11 of this report. All of these bonds are due between 2020 and 2038 . In connection with funding the BRW Term Loan Agreement, the Company entered into an agreement with Kingsland, pursuant to which, in return for Kingsland's pledge of its 144.8 million common shares of AVH (which are eligible to be converted into the same number of preferred shares, which may be deposited with the depositary for AVH's American Depositary Receipts ("ADRs"), the class of AVH securities that trades on the New York Stock Exchange (the "NYSE"), in exchange for 18.1 million ADRs) and its consent to BRW's pledge of its AVH common shares to United under the BRW Term Loan Agreement and related agreements, United (1) granted to Kingsland the right to put its AVH common shares to United at market price on the fifth anniversary of the BRW Term Loan Agreement or upon certain sales of AVH common shares owned by BRW, including upon a foreclosure, and (2) guaranteed BRW's obligation to pay Kingsland the difference (which amount, if paid by United, will increase the BRW Term Loan by such amount) if the market price of AVH common shares on the fifth anniversary, or upon any such sale, as applicable, is less than $12 per ADR on the NYSE, for an aggregate maximum possible combined put payment and guarantee amount on the fifth anniversary of $217 million . In 2018, the Company recorded a liability of $31 million for the fair value of its guarantee to loan additional funds to BRW if required. Any such additional loans to BRW would be collateralized by BRW's AVH shares and other collateral. As of December 31, 2019 , United is the guarantor of $132 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 below for the Company's debt, and the Company would potentially be responsible for those costs under the guarantees. As of December 31, 2019, United had cash collateralized $73 million of letters of credit, which generally have evergreen clauses and are expected to be renewed on an annual basis. As of December 31, 2019, United also had $414 million of surety bonds securing various obligations with expiration dates through 2023. Increased Cost Provisions. In United's financing transactions that include loans in which United is the borrower, United typically agrees to reimburse lenders for any reduced returns with respect to the loans due to any change in capital requirements and, in the case of loans with respect to which the interest rate is based on LIBOR, for certain other increased costs that the lenders incur in carrying these loans as a result of any change in law, subject, in most cases, to obligations of the lenders to take certain limited steps to mitigate the requirement for, or the amount of, such increased costs. At December 31, 2019, the Company had $3.4 billion of floating rate debt with remaining terms of up to 11 years that are subject to these increased cost provisions. In several financing transactions involving loans or leases from non-U.S. entities, with remaining terms of up to 11 years and an aggregate balance of $3.2 billion , the Company bears the risk of any change in tax laws that would subject loan or lease payments thereunder to non-U.S. entities to withholding taxes, subject to customary exclusions. Fuel Consortia. United participates in numerous fuel consortia with other air carriers at major airports to reduce the costs of fuel distribution and storage. Interline agreements govern the rights and responsibilities of the consortia members and provide for the allocation of the overall costs to operate the consortia based on usage. The consortia (and in limited cases, the participating carriers) have entered into long-term agreements to lease certain airport fuel storage and distribution facilities that are typically financed through tax-exempt bonds, either special facilities lease revenue bonds or general airport revenue bonds, issued by various local municipalities. In general, each consortium lease agreement requires the consortium to make lease payments in amounts sufficient to pay the maturing principal and interest payments on the bonds. As of December 31, 2019, approximately $1.9 billion principal amount of such bonds were secured by significant fuel facility leases in which United participates, as to which United and each of the signatory airlines has provided indirect guarantees of the debt. As of December 31, 2019, the Company's contingent exposure was approximately $175 million principal amount of such bonds based on its recent consortia participation. The Company's contingent exposure could increase if the participation of other air carriers decreases. The guarantees will expire when the tax-exempt bonds are paid in full, which ranges from 2022 to 2051 . The Company did not record a liability at the time these indirect guarantees were made. Regional Capacity Purchase. As of December 31, 2019 , United had 325 call options to purchase regional jet aircraft being operated by certain of its regional carriers with contract dates extending until 2029 . These call options are exercisable upon wrongful termination or breach of contract, among other conditions. Credit Card Processing Agreements. The Company has agreements with financial institutions that process customer credit card transactions for the sale of air travel and other services. Under certain of the Company's credit card processing agreements, the financial institutions in certain circumstances have the right to require that the Company maintain a reserve equal to a portion of advance ticket sales that has been processed by that financial institution, but for which the Company has not yet provided the air transportation. Such financial institutions may require additional cash or other collateral reserves to be established or additional withholding of payments related to receivables collected if the Company does not maintain certain minimum levels of unrestricted cash, cash equivalents and short-term investments (collectively, "Unrestricted Liquidity"). The Company's current level of Unrestricted Liquidity is substantially in excess of these minimum levels. Labor Negotiations. As of December 31, 2019 , United, including its subsidiaries, had approximately 96,000 employees. Approximately 84% of United's employees were represented by various U.S. labor organizations as of December 31, 2019 . On February 1, 2019, the collective bargaining agreement with the Air Line Pilots Association ("ALPA"), the labor union representing United's pilots, became amendable. The Company and ALPA are in negotiations for an amended agreement. The Company and UNITE HERE, the labor union representing United's Catering Operations employees, started negotiations for a first collective bargaining agreement in March 2019. The collective bargaining agreement with the International Brotherhood of Teamsters (the "IBT") contains provisions that require the Company to align contract terms with other airlines' workgroups under certain conditions. There were no triggering events in 2019 that invoked these provisions.

Special Charges and Unrealized

Special Charges and Unrealized (Gains) Losses on Investments	12 Months Ended
	Dec. 31, 2019
Restructuring and Related Activities [Abstract]
SPECIAL CHARGES AND UNREALIZED (GAINS) LOSSES ON INVESTMENTS	SPECIAL CHARGES AND UNREALIZED (GAINS) LOSSES ON INVESTMENTS Special charges and unrealized gains and losses on investments in the statements of consolidated operations consisted of the following for the years ended December 31 (in millions): Operating: 2019 2018 2017 Impairment of assets $ 171 $ 377 $ 25 Severance and benefit costs 16 41 116 Termination of an engine maintenance service agreement — 64 — (Gains) losses on sale of assets and other special charges 59 5 35 Total operating special charges 246 487 176 Nonoperating unrealized (gains) losses on investments (153 ) 5 — Total special charges and unrealized (gains) losses on investments 93 492 176 Income tax benefit (21 ) (110 ) (63 ) Income tax adjustments (Note 6) — (5 ) (189 ) Total special charges and unrealized (gains) losses on investments, net of income taxes and income tax adjustments $ 72 $ 377 $ (76 ) 2019 The Company conducted its annual impairment review of intangible assets in the fourth quarter of 2019, which consisted of a comparison of the book value of specific assets to the fair value of those assets. Due to a decrease in demand for the Hong Kong market and the resulting decrease in unit revenue, the Company determined that the value of its Hong Kong routes had been fully impaired. Accordingly, in the fourth quarter of 2019, the Company recorded a special non-cash impairment charge of $90 million associated with its Hong Kong routes. Notwithstanding the impairment, the collateral pledged under the Company's term loan continues to be sufficient to satisfy the loan covenants. The Company determined the fair value of the Hong Kong routes using a variation of the income approach known as the excess earnings method, which discounts an asset's projected future net cash flows to determine the current fair value. Assumptions used in the discounted cash flow methodology include a discount rate, which is based upon the Company's current weighted average cost of capital plus an asset-specific risk factor, and a projection of sales, expenses, gross margin, tax rates and contributory asset charges for several future years and a terminal growth rate. The assumptions used for future projections are determined based upon the Company's asset-specific forecasts along with the Company's strategic plan. These assumptions are inherently uncertain as they relate to future events and circumstances. Actual results will be influenced by the competitive environment, fuel costs and other expenses, and potentially other unforeseen events or circumstances that could have a material negative impact on future results. During 2019 , the Company recorded a $43 million impairment primarily for surplus Boeing 767 aircraft engines removed from operations, an $18 million charge primarily for the write-off of unexercised aircraft purchase options, and $20 million in other aircraft impairments. During 2019 , the Company recorded $14 million of management severance and $2 million of severance and benefit costs related to a voluntary early-out program for its technicians and related employees represented by the IBT. In the first quarter of 2017, approximately 1,000 technicians and related employees elected to voluntarily separate from the Company and received a severance payment, with a maximum value of $100,000 per participant, based on years of service, with retirement dates through early 2019. During 2019 , the Company recorded charges of $25 million related to contract terminations, $18 million for the settlement of certain legal matters, $14 million for costs related to the transition of fleet types within a regional carrier contract and $2 million of other charges. During 2019 , the Company recorded gains of $140 million for the change in market value of certain of its equity investments, primarily Azul, and $13 million for the change in fair value of the AVH Derivative Assets. 2018 During 2018, the Company recorded a special non-cash impairment charge of $206 million associated with its Hong Kong routes as a result of its annual intangible assets impairment review. The Company determined the fair value of the Hong Kong routes using a variation of the income approach as described above for the 2019 Hong Kong impairment. In May 2018, the Brazil–United States open skies agreement was ratified, which provides air carriers with unrestricted access between the United States and Brazil. The Company determined that the approval of the open skies agreement impaired the entire value of its Brazil route authorities because the agreement removes all limitations or reciprocity requirements for flights between the United States and Brazil. Accordingly, the Company recorded a $105 million special charge to write off the entire value of the intangible asset associated with its Brazil routes. Also during 2018, the Company recorded $66 million of fair value adjustments related to aircraft purchased off lease, write-offs of unexercised aircraft purchase options and other impairments related to certain fleet types and international slots no longer in use. During 2018, the Company recorded $22 million of severance and benefit costs related to the voluntary early-out program for its technicians and related employees represented by the IBT as described above. Also during 2018, the Company recorded other management severance of $19 million . During 2018, the Company recorded a one-time termination charge of $64 million related to one of its engine maintenance service agreements. During 2018, the Company recorded gains of $28 million for the change in market value of certain of its equity investments, primarily Azul. Also, the Company recorded losses of $33 million for the change in fair value of the AVH Derivative Assets. 2017 During 2017, the Company recorded a $10 million impairment charge related to obsolete spare parts inventory and a $15 million intangible asset impairment charge related to a maintenance service agreement. During 2017, the Company recorded $83 million of severance and benefit costs related to the voluntary early-out program for its technicians and related employees represented by the IBT as described above. Also during 2017, the Company recorded $33 million of other management severance. During 2017, the Company recorded charges of $12 million for weather-related damages, $11 million for losses on the sale of assets, and $12 million of other charges.

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) Quarter Ended (In millions, except per share amounts) March 31 June 30 September 30 December 31 2019 Operating revenue $ 9,589 $ 11,402 $ 11,380 $ 10,888 Income from operations 495 1,472 1,473 861 Net income 292 1,052 1,024 641 Basic earnings per share 1.09 4.03 4.01 2.54 Diluted earnings per share 1.09 4.02 3.99 2.53 2018 Operating revenue $ 9,032 $ 10,777 $ 11,003 $ 10,491 Income from operations (a) 262 1,145 1,187 635 Net income (a) 145 683 833 461 Basic earnings per share (a) 0.51 2.48 3.06 1.70 Diluted earnings per share (a) 0.51 2.48 3.05 1.69 (a) Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 of this report for additional information on the adjustments. 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 2019 Impairment of assets 8 61 — 102 Severance and benefit costs 6 6 2 2 (Gains) losses on sale of assets and other special charges 4 4 25 26 Total operating special charges 18 71 27 130 Nonoperating unrealized (gains) losses on investments (17 ) (34 ) (21 ) (81 ) Total special charges and unrealized (gains) losses on investments 1 37 6 49 Income tax benefit related to special charges and unrealized (gains) losses on investments — (8 ) (2 ) (11 ) Total special charges and unrealized (gains) losses on investments, net of income tax 1 29 4 38 2018 Impairment of assets $ 23 $ 111 $ 11 $ 232 Termination of an engine maintenance service agreement — — — 64 Severance and benefit costs 14 11 9 7 (Gains) losses on sale of assets and other special charges 3 7 (3 ) (2 ) Total operating special charges 40 129 17 301 Nonoperating unrealized (gains) losses on investments (45 ) 135 (29 ) (56 ) Total special charges and unrealized (gains) losses on investments (5 ) 264 (12 ) 245 Income tax benefit related to special charges and unrealized (gains) losses on investments 1 (59 ) 3 (55 ) Income tax adjustments — — — (5 ) Total special charges and unrealized (gains) losses on investments, net of income tax $ (4 ) $ 205 $ (9 ) $ 185 See Note 14 of this report for additional information related to these items.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS In December 2019 , a novel strain of coronavirus ("COVID-19") was reported in Wuhan, China. The World Health Organization has declared COVID-19 to constitute a "Public Health Emergency of International Concern." On January 30, 2020 , the U.S. Department of State issued a Level 4 "do not travel" advisory for China. The U.S. government has also implemented enhanced screenings, quarantine requirements and travel restrictions in connection with the COVID-19 outbreak. The Company has suspended its flights between the United States and each of Beijing, Chengdu, Shanghai and Hong Kong through April 24, 2020 . These routes represented approximately 5% of the Company's 2020 planned capacity and the Company's other trans-Pacific routes represented an additional 10% of the Company's 2020 planned capacity. As of the date of this report, the Company is experiencing an approximately 100% decline in near-term demand to China and an approximately 75% decline in near-term demand on the rest of the Company's trans-Pacific routes. The extent of the impact of the COVID-19 on the Company's operational and financial performance will depend on future developments, including the duration and spread of the outbreak and related travel advisories and restrictions and the impact of the COVID-19 on overall demand for air travel, all of which are highly uncertain and cannot be predicted. If traffic on the Company's trans-Pacific routes were to remain at these levels for an extended period, and/or routes in other parts of the Company's network begin to see significant declines in demand, our results of operations for full year 2020 may be materially adversely affected. In February 2020 , the Company announced that they had entered into a Third Amended and Restated Co-Branded Card Marketing Services Agreement (as amended from time to time, the "Agreement") with Chase. The Agreement, which replaces the Co-Brand Agreement, also extends the term into 2029

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2019
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Accounts	Schedule II Valuation and Qualifying Accounts For the Years Ended December 31, 2019 , 2018 and 2017 (In millions) Description Balance at Beginning of Period Additions Charged to Costs and Expenses Deductions Other Balance at End of Period Allowance for doubtful accounts: 2019 $ 8 $ 17 $ 16 $ — $ 9 2018 7 17 16 — 8 2017 10 20 23 — 7 Obsolescence allowance—spare parts: 2019 $ 412 $ 76 $ 63 $ — $ 425 2018 354 73 15 — 412 2017 295 75 17 1 354 Valuation allowance for deferred tax assets: 2019 $ 59 $ — $ 1 $ — $ 58 2018 63 2 6 — 59 2017 68 11 27 11 63

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates— The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America ("GAAP") requires management to make estimates and assumptions that affect the amounts reported in these financial statements and accompanying notes. Actual results could differ from those estimates.
Revenue Recognition	Revenue Recognition— The Company presents Passenger revenue, Cargo revenue and Other operating revenue on its income statement. Passenger revenue is recognized when transportation is provided and Cargo revenue is recognized when shipments arrive at their destination. Other operating revenue is recognized as the related performance obligations are satisfied. Passenger tickets and related ancillary services sold by the Company for mainline and regional flights are purchased primarily via credit card transactions, with payments collected by the Company in advance of the performance of related services. The Company initially records ticket sales in its Advance ticket sales liability, deferring revenue recognition until the travel occurs. For travel that has more than one flight segment, the Company deems each segment as a separate performance obligation and recognizes revenue for each segment as travel occurs. Tickets sold by other airlines where the Company provides the transportation are recognized as passenger revenue at the estimated value to be billed to the other airline when travel is provided. Differences between amounts billed and the actual amounts may be rejected and rebilled or written off if the amount recorded was different from the original estimate. When necessary, the Company records a reserve against its billings and payables with other airlines based on historical experience. The Company sells certain tickets with connecting flights with one or more segments operated by its other airline partners. For segments operated by its other airline partners, the Company has determined that it is acting as an agent on behalf of the other airlines as they are responsible for their portion of the contract (i.e. transportation of the passenger). The Company, as the agent, recognizes revenue within Other operating revenue at the time of the travel for the net amount representing commission to be retained by the Company for any segments flown by other airlines. Refundable tickets expire after one year from the date of issuance. Non-refundable tickets generally expire on the date of the intended travel, unless the date is extended by notification from the customer on or before the intended travel date. The Company records breakage revenue on the travel date for its estimate of tickets that will expire unused. To determine breakage, the Company uses its historical experience with refundable and nonrefundable expired tickets and other facts, such as recent aging trends, program changes and modifications that could affect the ultimate expiration patterns of tickets. Fees charged in association with changes or extensions to non-refundable tickets are considered part of the Company's passenger travel obligation. As such, those fees are deferred at the time of collection and recognized at the time the travel is provided. United initially capitalizes the costs of selling airline travel tickets and then recognizes those costs as Distribution expense at the time of travel. Passenger ticket costs include credit card fees, travel agency and other commissions paid, as well as global distribution systems booking fees. Advance Ticket Sales. Advance ticket sales represent the Company's liability to provide air transportation in the future. In the years ended December 31, 2019 and 2018 , the Company recognized approximately $3.4 billion and $3.1 billion , respectively, of passenger revenue for tickets that were included in Advance ticket sales at the beginning of those periods. All tickets sold at any given point of time have travel dates extending up to 12 months. As a result, the balance of the Company's Advance ticket sales liability represents activity that will be recognized in the next 12 months. Revenue by Geography. The Company further disaggregates revenue by geographic regions. 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 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. Ancillary Fees.
Ticket Taxes	Certain governmental taxes are imposed on the Company's ticket sales through a fee included in ticket prices. The Company collects these fees and remits them to the appropriate government agency. These fees are recorded on a net basis and, as a result, are excluded from revenue.
Frequent Flyer Accounting	Frequent Flyer Accounting— United's MileagePlus loyalty program builds customer loyalty by offering awards, benefits and services to program participants. Members in this program earn miles for travel on United, United Express, Star Alliance members and certain other airlines that participate in the program. Members can also earn miles by purchasing goods and services from our network of non-airline partners. We have contracts to sell miles to these partners with the terms extending from one to nine years . These partners include domestic and international credit card issuers, retail merchants, hotels, car rental companies and our participating airline partners. Miles can be redeemed for free (other than taxes and government-imposed fees), discounted or upgraded air travel and non-travel awards. Miles Earned in Conjunction with Travel. When frequent flyers earn miles for flights, the Company recognizes a portion of the ticket sales as revenue when the travel occurs and defers a portion of the ticket sale representing the value of the related miles as a separate performance obligation. The Company determines the estimated selling price of travel 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. At the time of travel, the Company records the portion allocated to the miles to Frequent flyer deferred revenue on the Company's consolidated balance sheet and subsequently recognizes it into revenue when miles are redeemed for air travel and non-air travel awards. Estimate of Miles Not Expected to be Redeemed . The Company's estimated selling price of miles is based on an equivalent ticket value less breakage, 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 breakage that considers a number of factors, including redemption patterns of various customer groups. The Company's breakage model is based on the assumption that the likelihood that an account will redeem its miles can be estimated based on a consideration of the account's historical behavior. The Company uses a logit regression model to estimate the probability that an account will redeem its current miles balance. The Company reviews its breakage estimates annually based upon the latest available information. The Company's estimate of the expected breakage of miles requires significant management judgment. Current and future changes to breakage assumptions, 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 program. For the portion of the outstanding miles that we estimate will not be redeemed, we recognize the associated value proportionally as the remaining miles are redeemed. Co-Brand Agreement . United has a significant contract (the "Co-Brand Agreement") to sell MileagePlus miles to its co-branded credit card partner JPMorgan Chase Bank, N.A. ("Chase"). Chase awards miles to MileagePlus members based on their credit card activity. United identified the following significant separately identifiable performance obligations in the Co-Brand Agreement: • MileagePlus miles awarded – United has a performance obligation to provide MileagePlus cardholders with miles to be used for air travel and non-travel award redemptions. The Company records Passenger revenue related to the travel awards when the transportation is provided and records Other revenue related to the non-travel awards when the goods or services are delivered. The Company records the cost associated with non-travel awards in Other operating revenue. • Marketing – United has a performance obligation to provide Chase access to United's customer list and the use of United's brand. Marketing revenue is recorded to Other operating revenue as miles are delivered to Chase. • Advertising – United has a performance obligation to provide advertising in support of the MileagePlus card in various customer contact points such as United's website, email promotions, direct mail campaigns, airport advertising and in-flight advertising. Advertising revenue is recorded to Other operating revenue as miles are delivered to Chase. • Other travel-related benefits – United's performance obligations are comprised of various items such as waived bag fees, seat upgrades and lounge passes. Lounge passes are recorded to Other operating revenue as customers use the lounge passes. Bag fees and seat upgrades are recorded to Passenger revenue at the time of the associated travel. We account for all the payments received (including monthly and one-time payments) under the Co-Brand Agreement by allocating them to the separately identifiable performance obligations. The fair value of the separately identifiable performance obligations is determined using management's estimated selling price of each component. 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 Agreement in order to determine the allocation of proceeds to each of the components to be delivered. We also evaluate volumes on an annual basis, which may result in a change in the allocation of the estimated consideration from the Co-Brand Agreement on a prospective basis. Frequent Flyer Deferred Revenue.
Cash and Cash Equivalents and Restricted Cash	Cash and Cash Equivalents and Restricted Cash— Highly liquid investments with a maturity of three months or less on their acquisition date are classified as cash and cash equivalents. Restricted cash primarily includes cash collateral for letters of credit and collateral associated with obligations for facility leases and other insurance-related obligations. 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.
Investments	Investments— Debt investments are classified as available-for-sale and are stated at fair value. Realized gains and losses on sales of these investments are reflected in Miscellaneous, net in the consolidated statements of operations. Unrealized gains and losses on available-for-sale securities are reflected as a component of accumulated other comprehensive income (loss). Equity investments with readily determinable fair values are measured at fair value. Equity investments without readily determinable fair values are measured using the equity method, or measured at cost with adjustments for observable changes in price or impairments (referred to as the measurement alternative). Changes in fair value are recorded in Unrealized gains (losses) on investments, net in the consolidated statements of operations.
Accounts Receivable	Accounts Receivable—
Aircraft Fuel, Spare Parts and Supplies	Aircraft Fuel, Spare Parts and Supplies— The Company accounts for aircraft fuel, spare parts and supplies at average cost and provides an obsolescence allowance for aircraft spare parts with an assumed residual value of 10% of original cost.
Property and Equipment	Property and Equipment— The Company records additions to owned operating property and equipment at cost when acquired. Property under finance leases and the related obligation for future lease payments are recorded at an amount equal to the initial present value of those lease payments. Modifications that enhance the operating performance or extend the useful lives of airframes or engines are capitalized as property and equipment. It is the Company's policy to record contractual damages received related to delays in delivery of aircraft as a reduction of the cost of the related aircraft.
Long-Lived Asset Impairments	Long-Lived Asset Impairments— The Company evaluates the carrying value of long-lived assets subject to amortization whenever events or changes in circumstances indicate that an impairment may exist. For purposes of this testing, the Company has generally identified the aircraft fleet type as the lowest level of identifiable cash flows. An impairment charge is recognized when the asset's carrying value exceeds its net undiscounted future cash flows and its fair market value. The amount of the charge is the difference between the asset's carrying value and fair market value. See Note 14 of this report for additional information related to impairments.
Intangibles	Intangibles—
Labor Costs	Labor Costs— The Company records expenses associated with new or amendable labor agreements when the amounts are probable and estimable. These include costs associated with lump sum cash payments that would be made in conjunction with the ratification of labor agreements. To the extent these upfront costs are in lieu of future pay increases, they would be capitalized and amortized over the term of the labor agreements. If not, these amounts would be expensed.
Share-Based Compensation	Share-Based Compensation— The Company measures the cost of employee services received in exchange for an award of equity instruments based on the grant date fair value of the award. The resulting cost is recognized over the period during which an employee is required to provide service in exchange for the award, usually the vesting period. Obligations for cash-settled restricted stock units ("RSUs") are remeasured at fair value throughout the requisite service period at the close of the reporting period based upon UAL's stock price. In addition to the service requirement, certain RSUs have performance metrics that must be achieved prior to vesting. These awards are accrued based on the expected level of achievement at each reporting period. An adjustment is recorded each reporting period to adjust compensation expense based on the then current level of expected performance achievement for the performance-based awards. See Note 4 of this report for additional information on UAL's share-based compensation plans.
Maintenance and Repairs	Maintenance and Repairs— The cost of maintenance and repairs, including the cost of minor replacements, is charged to expense as incurred, except for costs incurred under our power-by-the-hour ("PBTH") engine maintenance agreements. PBTH contracts transfer certain risk to third-party service providers and fix the amount we pay per flight hour or per cycle to the service provider in exchange for maintenance and repairs under a predefined maintenance program. Under PBTH agreements, the Company recognizes expense at a level rate per engine hour, unless the level of service effort and the related payments during the period are substantially consistent, in which case the Company recognizes expense based on the amounts paid.
Advertising	Advertising—
Third-Party Business	Third-Party Business— The Company has third-party business revenue that includes fuel sales, catering, ground handling, maintenance services and frequent flyer award non-travel redemptions. Third-party business revenue is recorded in Other operating revenue. The Company also incurs third-party business expenses, such as maintenance, ground handling and catering services for third parties, fuel sales and non-travel mileage redemptions. The third-party business expenses are recorded in Other operating expenses, except for non-travel mileage redemption. Non-travel mileage redemption expenses are recorded to Other operating revenue.
Uncertain Income Tax Positions	Uncertain Income Tax Positions—
Recently Issued Accounting Standards	Recently Issued Accounting Standards— The Company adopted Financial Accounting Standards Board ("FASB") Accounting Standards Codification Topic 842, Leases (the "New Lease Standard"), effective January 1, 2019. The Company used the modified retrospective approach for all leases existing at or commencing after January 1, 2017 and elected the package of transition practical expedients for expired or existing contracts, which does not require reassessment of: (1) whether any of our contracts are or contain leases, (2) lease classification and (3) initial direct costs. The New Lease Standard prescribes that an entity should recognize a right-of-use asset and a lease liability for all leases at the commencement date of each lease and recognize expenses on their income statements similar to the prior FASB Accounting Standards Codification Topic 840, Leases ("Topic 840"). The adoption of the New Lease Standard had the same impact on the financial statements of United as it had on the financial statements of UAL. The table below presents the impact of the adoption of the New Lease Standard on select accounts and captions of UAL's statement of consolidated operations for the year ended December 31 (in millions, except per share amounts): As Reported New Lease Standard Adjustments As Adjusted 2018 2017 2018 2017 2018 2017 Regional capacity purchase $ 2,601 $ 2,232 $ 48 $ 36 $ 2,649 $ 2,268 Landing fees and other rent 2,359 2,240 90 70 2,449 2,310 Depreciation and amortization 2,240 2,149 (75 ) (53 ) 2,165 2,096 Interest expense (729 ) (671 ) 59 45 (670 ) (626 ) Interest capitalized 70 84 (5 ) (10 ) 65 74 Income tax expense 529 896 (3 ) (16 ) 526 880 Net income 2,129 2,144 (7 ) (1 ) 2,122 2,143 Earnings per share, basic 7.73 7.08 (0.03 ) — 7.70 7.08 Earnings per share, diluted 7.70 7.06 (0.03 ) — 7.67 7.06 The expense for leases under the New Lease Standard will continue to be classified in their historical income statement captions (primarily in Aircraft rent, Landing fees and other rent and Regional capacity purchase in our statements of consolidated operations). The adoption of the New Lease Standard resulted in the recharacterization of certain leases from capital leases under Topic 840 to operating leases under the New Lease Standard. This change resulted in less depreciation and amortization and interest expense associated with capital leases offset by higher lease expense associated with operating leases. The recharacterization is associated with leases of certain airport facilities that were derecognized as part of the build-to-suit transition guidance under the New Lease Standard. The reduction in capitalized interest is also associated with the same airport facilities leases. The table below presents the impact of the adoption of the New Lease Standard on UAL's balance sheet accounts and captions (in millions): December 31, 2018 As Reported New Lease Standard Adjustments As Adjusted Receivables, less allowance for doubtful accounts $ 1,346 $ 80 $ 1,426 Prepaid expenses and other 913 (180 ) 733 Flight equipment, owned and finance leases (a) 32,636 (37 ) 32,599 Other property and equipment, owned and finance leases (a) 7,930 (1,041 ) 6,889 Accumulated depreciation and amortization, owned and finance leases (a) (13,414 ) 148 (13,266 ) Operating lease right-of-use assets — 5,262 5,262 Current maturities of finance leases (a) 149 (26 ) 123 Current maturities of operating leases — 719 719 Other current liabilities 619 (66 ) 553 Long-term obligations under finance leases (a) 1,134 (910 ) 224 Long-term obligations under operating leases — 5,276 5,276 Deferred income taxes 814 14 828 Other long-term liabilities 1,832 (822 ) 1,010 Retained earnings 6,668 47 6,715 (a) Finance leases, under the New Lease Standard, are the equivalent of capital leases under Topic 840. The table below presents the impact of the adoption of the New Lease Standard on select line items of UAL's statement of consolidated cash flows for the year ended December 31 (in millions): As Reported New Lease Standard Adjustments As Adjusted 2018 2017 2018 2017 2018 2017 Cash Flows from Operating Activities: Net cash provided by operating activities $ 6,181 $ 3,413 $ (17 ) $ 61 $ 6,164 $ 3,474 Cash Flows from Investing Activities: Capital expenditures (4,177 ) (3,998 ) 107 128 (4,070 ) (3,870 ) Cash Flows from Financing Activities: Proceeds from issuance of long-term debt 1,740 2,765 (146 ) (228 ) 1,594 2,537 Principal payments under finance leases (134 ) (124 ) 55 40 (79 ) (84 ) The adoption of the New Lease Standard primarily resulted in the recording of assets and liabilities of our operating leases on our consolidated balance sheets. Certain amounts recorded for prepaid and accrued rent associated with historical operating leases were reclassified to the newly captioned Operating lease right-of-use assets in the consolidated balance sheets. Also, certain leases designated under Topic 840 as owned assets and capital leases are not considered to be assets under the New Lease Standard and have been removed from the consolidated balance sheets, along with the related capital lease liability, due to the leases having variable lease payments. In June 2016, the FASB issued Accounting Standards Update No. 2016-13, Financial Instruments-Credit Losses ("ASU 2016-13"). The amendments in this update replace the incurred loss methodology with a methodology that reflects expected credit losses. This update requires financial assets measured at amortized cost basis, such as trade receivables, loans and held-to-maturity debt securities, to be presented at the net amount expected to be collected, and requires entities to record expected losses for certain guarantees and off-balance sheet exposures. The update also eliminates the concept of other-than-temporary impairment for available-for-sale securities. Impairments on available-for-sale securities will be required to be recognized in earnings through an allowance when the fair value is less than amortized cost and a credit loss exists, or the securities are expected to be sold before recovery of amortized cost. The Company adopted ASU 2016-13 on January 1, 2020. The standard update is not expected to have a material impact on the Company's consolidated financial statements.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Operating Revenue by Principal 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): 2019 2018 2017 Domestic (U.S. and Canada) $ 26,960 $ 25,552 $ 23,114 Atlantic 7,387 7,103 6,340 Pacific 5,132 5,188 4,914 Latin America 3,780 3,460 3,416 Total $ 43,259 $ 41,303 $ 37,784
Roll Forward of Frequent Flyer Deferred Revenue	The table below presents a roll forward of Frequent flyer deferred revenue (in millions): Twelve Months Ended 2019 2018 Total Frequent flyer deferred revenue - beginning balance $ 5,005 $ 4,783 Total miles awarded 2,621 2,451 Travel miles redeemed (Passenger revenue) (2,213 ) (2,068 ) Non-travel miles redeemed (Other operating revenue) (137 ) (161 ) Total Frequent flyer deferred revenue - ending balance $ 5,276 $ 5,005
Reconciliation of Cash, 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 (in millions): UAL United At December 31, At December 31, 2019 2018 2017 2019 2018 2017 Current assets: Cash and cash equivalents $ 2,762 $ 1,694 $ 1,482 $ 2,756 $ 1,688 $ 1,476 Restricted cash included in Prepaid expenses and other — — 18 — — 18 Other assets: Restricted cash 106 105 91 106 105 91 Total cash, cash equivalents and restricted cash shown in the statement of consolidated cash flows $ 2,868 $ 1,799 $ 1,591 $ 2,862 $ 1,793 $ 1,585
Reconciliation of Cash, 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 (in millions): UAL United At December 31, At December 31, 2019 2018 2017 2019 2018 2017 Current assets: Cash and cash equivalents $ 2,762 $ 1,694 $ 1,482 $ 2,756 $ 1,688 $ 1,476 Restricted cash included in Prepaid expenses and other — — 18 — — 18 Other assets: Restricted cash 106 105 91 106 105 91 Total cash, cash equivalents and restricted cash shown in the statement of consolidated cash flows $ 2,868 $ 1,799 $ 1,591 $ 2,862 $ 1,793 $ 1,585
Estimated Useful Lives of Property and Equipment	The estimated useful lives of property and equipment are as follows: Estimated Useful Life (in years) Aircraft, spare engines and related rotable parts 25 to 30 Aircraft seats 10 to 15 Buildings 25 to 45 Other property and equipment 3 to 15 Computer software 5 to 15 Building improvements 1 to 40
Information about Goodwill and Other Intangible Assets	The following table presents information about the Company's goodwill and other intangible assets at December 31 (in millions): 2019 2018 Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Goodwill $ 4,523 $ 4,523 Indefinite-lived intangible assets Route authorities $ 1,150 $ 1,240 Airport slots 546 546 Tradenames and logos 593 593 Alliances 404 404 Total $ 2,693 $ 2,783 Finite-lived intangible assets Frequent flyer database $ 1,177 $ 931 $ 1,177 $ 884 Hubs 145 104 145 97 Contracts 120 111 120 106 Other 314 294 314 293 Total $ 1,756 $ 1,440 $ 1,756 $ 1,380
Impact of the Adoption of the New Lease Standard	The adoption of the New Lease Standard had the same impact on the financial statements of United as it had on the financial statements of UAL. The table below presents the impact of the adoption of the New Lease Standard on select accounts and captions of UAL's statement of consolidated operations for the year ended December 31 (in millions, except per share amounts): As Reported New Lease Standard Adjustments As Adjusted 2018 2017 2018 2017 2018 2017 Regional capacity purchase $ 2,601 $ 2,232 $ 48 $ 36 $ 2,649 $ 2,268 Landing fees and other rent 2,359 2,240 90 70 2,449 2,310 Depreciation and amortization 2,240 2,149 (75 ) (53 ) 2,165 2,096 Interest expense (729 ) (671 ) 59 45 (670 ) (626 ) Interest capitalized 70 84 (5 ) (10 ) 65 74 Income tax expense 529 896 (3 ) (16 ) 526 880 Net income 2,129 2,144 (7 ) (1 ) 2,122 2,143 Earnings per share, basic 7.73 7.08 (0.03 ) — 7.70 7.08 Earnings per share, diluted 7.70 7.06 (0.03 ) — 7.67 7.06 The expense for leases under the New Lease Standard will continue to be classified in their historical income statement captions (primarily in Aircraft rent, Landing fees and other rent and Regional capacity purchase in our statements of consolidated operations). The adoption of the New Lease Standard resulted in the recharacterization of certain leases from capital leases under Topic 840 to operating leases under the New Lease Standard. This change resulted in less depreciation and amortization and interest expense associated with capital leases offset by higher lease expense associated with operating leases. The recharacterization is associated with leases of certain airport facilities that were derecognized as part of the build-to-suit transition guidance under the New Lease Standard. The reduction in capitalized interest is also associated with the same airport facilities leases. The table below presents the impact of the adoption of the New Lease Standard on UAL's balance sheet accounts and captions (in millions): December 31, 2018 As Reported New Lease Standard Adjustments As Adjusted Receivables, less allowance for doubtful accounts $ 1,346 $ 80 $ 1,426 Prepaid expenses and other 913 (180 ) 733 Flight equipment, owned and finance leases (a) 32,636 (37 ) 32,599 Other property and equipment, owned and finance leases (a) 7,930 (1,041 ) 6,889 Accumulated depreciation and amortization, owned and finance leases (a) (13,414 ) 148 (13,266 ) Operating lease right-of-use assets — 5,262 5,262 Current maturities of finance leases (a) 149 (26 ) 123 Current maturities of operating leases — 719 719 Other current liabilities 619 (66 ) 553 Long-term obligations under finance leases (a) 1,134 (910 ) 224 Long-term obligations under operating leases — 5,276 5,276 Deferred income taxes 814 14 828 Other long-term liabilities 1,832 (822 ) 1,010 Retained earnings 6,668 47 6,715 (a) Finance leases, under the New Lease Standard, are the equivalent of capital leases under Topic 840. The table below presents the impact of the adoption of the New Lease Standard on select line items of UAL's statement of consolidated cash flows for the year ended December 31 (in millions): As Reported New Lease Standard Adjustments As Adjusted 2018 2017 2018 2017 2018 2017 Cash Flows from Operating Activities: Net cash provided by operating activities $ 6,181 $ 3,413 $ (17 ) $ 61 $ 6,164 $ 3,474 Cash Flows from Investing Activities: Capital expenditures (4,177 ) (3,998 ) 107 128 (4,070 ) (3,870 ) Cash Flows from Financing Activities: Proceeds from issuance of long-term debt 1,740 2,765 (146 ) (228 ) 1,594 2,537 Principal payments under finance leases (134 ) (124 ) 55 40 (79 ) (84 )

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
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): 2019 2018 (a) 2017 (a) Earnings available to common stockholders $ 3,009 $ 2,122 $ 2,143 Basic weighted-average shares outstanding 258.8 275.5 302.7 Effect of employee stock awards 1.1 1.2 0.9 Diluted weighted-average shares outstanding 259.9 276.7 303.6 Earnings per share, basic $ 11.63 $ 7.70 $ 7.08 Earnings per share, diluted $ 11.58 $ 7.67 $ 7.06 (a) Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 of this report for additional information on the adjustments.

Share-Based Compensation Plans

Share-Based Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Information Related to 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): 2019 2018 2017 Compensation cost: RSUs $ 98 $ 98 $ 63 Restricted stock 1 2 8 Stock options 1 1 2 Total $ 100 $ 101 $ 73
Summary of Unearned Compensation and Weighted-Average Remaining Period to Recognize Costs	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, 2019 (in millions, except as noted): Unearned Compensation Weighted-Average Remaining Period (in years) RSUs $ 66 2.0 Stock options 11 5.3 Total $ 77
Summary of RSU and Restricted Stock Activity	The table below summarizes UAL's RSUs and restricted stock activity for the years ended December 31 (shares in millions): Liability Awards Equity Awards RSUs RSUs Weighted- Average Grant Price Restricted Stock Weighted- Average Grant Price Outstanding at December 31, 2016 2.1 0.8 $ 51.67 0.5 $ 52.00 Granted 0.6 1.0 71.68 — — Vested (0.7 ) (0.3 ) 51.81 (0.2 ) 51.60 Forfeited (0.2 ) (0.1 ) 57.49 — — Outstanding at December 31, 2017 1.8 1.4 63.99 0.3 52.30 Granted 0.7 1.1 67.74 — — Vested (0.5 ) (0.5 ) 63.02 (0.2 ) 53.24 Forfeited (0.1 ) (0.2 ) 67.34 — — Outstanding at December 31, 2018 1.9 1.8 66.29 0.1 51.17 Granted 0.1 1.1 86.72 — — Vested (0.5 ) (0.8 ) 64.85 (0.1 ) 51.17 Forfeited (0.9 ) (0.1 ) 76.48 — — Outstanding at December 31, 2019 0.6 2.0 78.03 — —

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Components of AOCI	The tables below present the components of the Company's AOCI, net of tax (in millions): Pension and Other Postretirement Liabilities Investments and Other Deferred Taxes Total Balance at December 31, 2016 $ (854 ) $ (1 ) $ 26 $ (829 ) Change in value (306 ) (a) (7 ) 74 (239 ) Amounts reclassified to earnings 58 2 (21 ) 39 Reclassification of stranded tax effects — — (118 ) (b) (118 ) Balance at December 31, 2017 (1,102 ) (6 ) (39 ) (1,147 ) Change in value 377 (a) (5 ) (83 ) 289 Amounts reclassified to earnings 62 — (13 ) 49 Amounts reclassified to retained earnings ("RE") — 7 (c) (1 ) (c) 6 Balance at December 31, 2018 (663 ) (4 ) (136 ) (803 ) Change in value 105 (a) 7 (24 ) 88 Amounts reclassified to earnings (2 ) (1 ) — (3 ) Balance at December 31, 2019 $ (560 ) $ 2 $ (160 ) $ (718 ) (a) This AOCI component is included in the computation of net periodic pension and other postretirement costs. See Note 7 of this report for additional information on pensions and other postretirement liabilities. (b) This amount represents the reclassification from AOCI to RE of the stranded tax effects resulting from the enactment of the Tax Cuts and Jobs Act (the "Tax Act"). (c) These amounts represent the reclassification from AOCI to RE of the unrealized loss, and related tax, on the Company's investment in Azul Linhas Aéreas Brasileiras S.A. ("Azul") which was classified as an available-for-sale security prior to the Company adopting Accounting Standards Update No. 2016-01, Financial Instruments—Overall (Subtopic 825-10) effective January 1, 2018.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Tax Provision (Benefit) Differed from Amounts Computed at the Statutory Federal Income Tax Rate and 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 (in millions) : UAL 2019 2018 (a) 2017 (a) Income tax provision at statutory rate $ 822 $ 556 $ 1,058 State income taxes, net of federal income tax benefit 50 29 30 Foreign tax rate differential (90 ) (84 ) (43 ) Global intangible low-taxed income 90 4 — Foreign income taxes 1 2 3 Nondeductible employee meals 12 12 17 Impact of Tax Act — (5 ) (189 ) State rate change — 3 12 Valuation allowance (4 ) (3 ) (16 ) Other, net 24 12 8 $ 905 $ 526 $ 880 Current $ 23 $ 14 $ (77 ) Deferred 882 512 957 $ 905 $ 526 $ 880 United 2019 2018 (a) 2017 (a) Income tax provision at statutory rate $ 822 $ 557 $ 1,059 State income taxes, net of federal income tax 50 29 30 Foreign tax rate differential (90 ) (84 ) (43 ) Global intangible low-taxed income 90 4 — Foreign income taxes 1 2 3 Nondeductible employee meals 12 12 17 Impact of Tax Act — (5 ) (206 ) State rate change — 3 12 Valuation allowance (4 ) (3 ) (16 ) Other, net 24 12 8 $ 905 $ 527 $ 864 Current $ 23 $ 14 $ (77 ) Deferred 882 513 941 $ 905 $ 527 $ 864 (a) Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 of this report for additional information on the adjustments.
Temporary Differences and Carryforwards Giving Rise to Deferred Tax Assets and Liabilities	Temporary differences and carryforwards that give rise to deferred tax assets and liabilities at December 31, 2019 and 2018 were as follows (in millions): UAL United 2019 2018 2019 2018 Deferred income tax asset (liability): Federal and state net operating loss ("NOL") carryforwards $ 695 $ 398 $ 668 $ 371 Deferred revenue 1,287 1,232 1,287 1,232 Employee benefits, including pension, postretirement and medical 715 885 715 885 Operating lease liabilities 1,256 1,338 1,256 1,338 Other 165 229 165 229 Less: Valuation allowance (58 ) (59 ) (58 ) (59 ) Total deferred tax assets $ 4,060 $ 4,023 $ 4,033 $ 3,996 Depreciation $ (4,011 ) $ (2,929 ) $ (4,011 ) $ (2,929 ) Operating lease right-of-use asset (1,061 ) (1,173 ) (1,061 ) (1,173 ) Intangibles (724 ) (749 ) (724 ) (749 ) Total deferred tax liabilities $ (5,796 ) $ (4,851 ) $ (5,796 ) $ (4,851 ) Net deferred tax liability $ (1,736 ) $ (828 ) $ (1,763 ) $ (855 )

Pension and Other Postretirem_2

Pension and Other Postretirement Plans (Tables)	12 Months Ended
	Dec. 31, 2019
Retirement Benefits [Abstract]
Reconciliation of the Change in Benefit Obligation and Plan Assets and Funded Status	The following tables set 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 December 31, 2019 Year Ended December 31, 2018 Accumulated benefit obligation: $ 5,333 $ 4,448 Change in projected benefit obligation: Projected benefit obligation at beginning of year $ 5,396 $ 5,852 Service cost 184 228 Interest cost 226 217 Actuarial (gain) loss 784 (601 ) Gross benefits paid and settlements (200 ) (292 ) Other 8 (8 ) Projected benefit obligation at end of year $ 6,398 $ 5,396 Change in plan assets: Fair value of plan assets at beginning of year $ 3,827 $ 3,932 Actual (loss) return on plan assets 684 (215 ) Employer contributions 649 413 Gross benefits paid and settlements (200 ) (292 ) Other 4 (11 ) Fair value of plan assets at end of year $ 4,964 $ 3,827 Funded status—Net amount recognized $ (1,434 ) $ (1,569 ) Pension Benefits December 31, 2019 December 31, 2018 Amounts recognized in the consolidated balance sheets consist of: Noncurrent asset $ 14 $ 13 Current liability (2 ) (6 ) Noncurrent liability (1,446 ) (1,576 ) Total liability $ (1,434 ) $ (1,569 ) Amounts recognized in accumulated other comprehensive loss consist of: Net actuarial loss $ (1,652 ) $ (1,382 ) Prior service cost (4 ) (5 ) Total accumulated other comprehensive loss $ (1,656 ) $ (1,387 ) Other Postretirement Benefits Year Ended December 31, 2019 Year Ended December 31, 2018 Change in benefit obligation: Benefit obligation at beginning of year $ 1,391 $ 1,710 Service cost 10 12 Interest cost 47 61 Plan participants' contributions 67 68 Benefits paid (180 ) (181 ) Actuarial loss (gain) 99 (285 ) Plan amendments (597 ) — Other 5 6 Benefit obligation at end of year $ 842 $ 1,391 Change in plan assets: Fair value of plan assets at beginning of year $ 53 $ 54 Actual return on plan assets 1 1 Employer contributions 111 111 Plan participants' contributions 67 68 Benefits paid (180 ) (181 ) Fair value of plan assets at end of year 52 53 Funded status—Net amount recognized $ (790 ) $ (1,338 )
Amounts Recognized in Consolidated Balance Sheet and Accumulated Other Comprehensive Income (Loss)	Pension Benefits December 31, 2019 December 31, 2018 Amounts recognized in the consolidated balance sheets consist of: Noncurrent asset $ 14 $ 13 Current liability (2 ) (6 ) Noncurrent liability (1,446 ) (1,576 ) Total liability $ (1,434 ) $ (1,569 ) Amounts recognized in accumulated other comprehensive loss consist of: Net actuarial loss $ (1,652 ) $ (1,382 ) Prior service cost (4 ) (5 ) Total accumulated other comprehensive loss $ (1,656 ) $ (1,387 ) Other Postretirement Benefits Year Ended December 31, 2019 Year Ended December 31, 2018 Change in benefit obligation: Benefit obligation at beginning of year $ 1,391 $ 1,710 Service cost 10 12 Interest cost 47 61 Plan participants' contributions 67 68 Benefits paid (180 ) (181 ) Actuarial loss (gain) 99 (285 ) Plan amendments (597 ) — Other 5 6 Benefit obligation at end of year $ 842 $ 1,391 Change in plan assets: Fair value of plan assets at beginning of year $ 53 $ 54 Actual return on plan assets 1 1 Employer contributions 111 111 Plan participants' contributions 67 68 Benefits paid (180 ) (181 ) Fair value of plan assets at end of year 52 53 Funded status—Net amount recognized $ (790 ) $ (1,338 ) Other Postretirement Benefits December 31, 2019 December 31, 2018 Amounts recognized in the consolidated balance sheets consist of: Current liability $ (1 ) $ (43 ) Noncurrent liability (789 ) (1,295 ) Total liability $ (790 ) $ (1,338 ) Amounts recognized in accumulated other comprehensive income consist of: Net actuarial gain $ 403 $ 554 Prior service credit 693 170 Total accumulated other comprehensive income $ 1,096 $ 724
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): 2019 2018 Projected benefit obligation $ 6,161 $ 5,196 Accumulated benefit obligation 5,137 4,286 Fair value of plan assets 4,714 3,614
Components Of Net Periodic Benefit Cost	Net periodic benefit cost for the years ended December 31 included the following components (in millions): 2019 2018 2017 Pension Benefits Other Postretirement Benefits Pension Benefits Other Postretirement Benefits Pension Benefits Other Postretirement Benefits Service cost $ 184 $ 10 $ 228 $ 12 $ 195 $ 13 Interest cost 226 47 217 61 220 66 Expected return on plan assets (291 ) (1 ) (292 ) (2 ) (243 ) (2 ) Amortization of unrecognized actuarial (gain) loss 118 (52 ) 130 (32 ) 128 (33 ) Amortization of prior service credits — (73 ) — (37 ) — (37 ) Other 5 — 1 — 5 — Net periodic benefit cost (credit) $ 242 $ (69 ) $ 284 $ 2 $ 305 $ 7
Assumptions Used for Benefit Plans	The assumptions used for the benefit plans were as follows: Pension Benefits Assumptions used to determine benefit obligations 2019 2018 Discount rate 3.52 % 4.20 % Rate of compensation increase 3.89 % 3.89 % Assumptions used to determine net expense Discount rate 4.21 % 3.65 % Expected return on plan assets 7.40 % 7.31 % Rate of compensation increase 3.89 % 3.89 % Other Postretirement Benefits Assumptions used to determine benefit obligations 2019 2018 Discount rate 3.35 % 4.30 % Assumptions used to determine net expense Discount rate 4.30 % 3.63 % Expected return on plan assets 3.00 % 3.00 % Health care cost trend rate assumed for next year 6.00 % 6.00 % Rate to which the cost trend rate is assumed to decline (ultimate trend rate in 2033) 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 30-45 % 10 % Fixed-income securities 35-50 5 Alternatives 15-25 7
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): 2019 2018 Pension Plan Assets: Total Level 1 Level 2 Level 3 Assets Measured at NAV(a) Total Level 1 Level 2 Level 3 Assets Measured at NAV(a) Equity securities funds $ 1,957 $ 47 $ 117 $ 71 $ 1,722 $ 1,457 $ 254 $ 106 $ 63 $ 1,034 Fixed-income securities 1,732 — 687 69 976 1,520 — 628 87 805 Alternatives 776 — — 205 571 596 — — 134 462 Other investments 499 466 21 12 — 254 224 17 13 — Total $ 4,964 $ 513 $ 825 $ 357 $ 3,269 $ 3,827 $ 478 $ 751 $ 297 $ 2,301 Other Postretirement Benefit Plan Assets: Deposit administration fund $ 52 $ — $ — $ 52 $ — $ 53 $ — $ — $ 53 $ — (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. public- or private-sector entities. Redemption periods for these investments range from daily to semiannually.
Defined Benefit Plan Assets Measured at Fair Value Using Unobservable Inputs	The reconciliation of United's benefit plan assets measured at fair value using unobservable inputs (Level 3) for the years ended December 31, 2019 and 2018 is as follows (in millions): 2019 2018 Balance at beginning of year $ 350 $ 383 Actual return (loss) on plan assets: Sold during the year 12 10 Held at year end (1 ) (21 ) Purchases, sales, issuances and settlements (net) 48 (22 ) Balance at end of year $ 409 $ 350
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, 2019 are as follows (in millions): Pension Other Postretirement 2020 $ 361 $ 53 2021 386 56 2022 399 59 2023 410 62 2024 399 64 Years 2025 – 2029 2,219 328
Participation in the IAM National Pension Plan	United's participation in the IAM National Pension Plan ("IAM Plan") for the annual period ended December 31, 2019 is outlined in the table below. Except as described in table below, there have been no other changes that affect the comparability of 2019 and 2018 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 $467 million in employers' contributions for the year ended December 31, 2018 . For 2018 , the Company's contributions to the IAM Plan represented more than 5% of total contributions to the IAM Plan. The 2019 information is not available as Form 5500 is not final for the plan year. Pension Fund IAM National Pension Fund EIN/ Pension Plan Number 51-6031295 - 002 Pension Protection Act Zone Status (2019 and 2018) Red Zone (2019) and Green Zone (2018). Plans in the Green Zone are at least 80 percent funded. Plans in the Red Zone are less than 65% funded. The IAM National Pension Fund Board of Trustees voluntarily elected to place the fund in the Red Zone for 2019, although the fund was over 80% funded at the time, to protect the fund's participants' core retirement benefits and strengthen the fund's financial health over the long term. FIP/RP Status Pending/Implemented A 10-year Rehabilitation Plan effective, January 1, 2022, was adopted on April 17, 2019 that requires the Company to make an additional contribution of 2.5% of the hourly contribution rate, compounded annually for the length of the Rehabilitation Plan, effective June 1, 2019. United's Contributions $59 million, $52 million and $50 million in the years ended December 31, 2019, 2018 and 2017, respectively Surcharge Imposed No Expiration Date of Collective Bargaining Agreement N/A

Investments and Fair Value Me_2

Investments and Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
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): 2019 2018 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Cash and cash equivalents $ 2,762 $ 2,762 $ — $ — $ 1,694 $ 1,694 $ — $ — Short-term investments: Corporate debt 1,045 — 1,045 — 1,023 — 1,023 — Asset-backed securities 690 — 690 — 746 — 746 — U.S. government and agency notes 124 — 124 — 108 — 108 — Certificates of deposit placed through an account registry service ("CDARS") 35 — 35 — 75 — 75 — Other fixed-income securities 95 — 95 — 116 — 116 — Other investments measured at NAV 193 — — — 188 — — — Restricted cash 106 106 — — 105 105 — — Long-term investments: Equity securities 385 385 — — 249 249 — — AVH Derivative Assets 24 — — 24 11 — — 11
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). Carrying amounts include any related discounts, premiums and issuance costs: 2019 2018 Carrying Amount Fair Value Carrying Amount Fair Value Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Long-term debt $ 14,552 $ 15,203 $ — $ 11,398 $ 3,805 $ 13,445 $ 13,450 $ — $ 9,525 $ 3,925

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Summary of Long-Term Debt	(In millions) At December 31, 2019 2018 Secured Notes payable, fixed interest rates of 2.7% to 9.8% (weighted average rate of 3.95% as of December 31, 2019), payable through 2032 $ 9,615 $ 8,811 Notes payable, floating interest rates of the London interbank offered rate ("LIBOR") plus 1.05% to 2.25%, payable through 2030 1,970 2,051 Term loan, LIBOR plus 1.75%, or alternative rate based on certain market rates plus 0.75%, due 2024 1,459 1,474 Unsecured 6% Senior Notes due 2020 (a) 300 300 4.25% Senior Notes due 2022 (a) 400 400 5% Senior Notes due 2024 (a) 300 300 4.875% Senior Notes due 2025 (a) 350 — Other 339 300 14,733 13,636 Less: unamortized debt discount, premiums and debt issuance costs (181 ) (191 ) Less: current portion of long-term debt (1,407 ) (1,230 ) Long-term debt, net $ 13,145 $ 12,215 (a) UAL is the issuer of this debt. United is a guarantor.
Contractual Principal Payments under Outstanding Long-Term Debt Agreements	The table below presents the Company's contractual principal payments (not including debt discount or debt issuance costs) at December 31, 2019 under then-outstanding long-term debt agreements in each of the next five calendar years (in millions): 2020 $ 1,407 2021 1,415 2022 1,765 2023 815 2024 3,122 After 2024 6,209 $ 14,733
Details of Pass Through Trusts	Certain details of the pass-through trusts with proceeds received from issuance of debt in 2019 are as follows (in millions, except stated interest rate): EETC Issuance Date Class Principal Final expected distribution date Stated interest rate Total proceeds received from issuance of debt during 2019 and recorded as debt as of December 31, 2019 Amounts returned to the holders of the Pass-Through Certificates (a) Remaining proceeds from issuance of debt to be received in future periods September 2019 AA $ 702 May 2032 2.70% $ 513 $ — $ 189 September 2019 A 287 May 2028 2.90% 210 — 77 September 2019 B 232 May 2028 3.50% 170 — 62 February 2019 AA 717 August 2031 4.15% 651 66 — February 2019 A 296 August 2031 4.55% 269 27 — $ 2,234 $ 1,813 $ 93 $ 328 (a) These proceeds were expected to be used to purchase equipment notes issued by United and secured by three Boeing 737 MAX aircraft, which aircraft were scheduled for delivery by Boeing in 2019. However, as a result of the Federal Aviation Administration Order prohibiting the operation of Boeing 737 MAX series aircraft by U.S. certificated operators (the "FAA Order"), United did not take delivery of these aircraft. These amounts were distributed to the holders of February 2019 Pass Through Certificates together with accrued and unpaid interest thereon but without premium. As a result of the FAA Order, the Company did not contemplate using any proceeds from the September 2019 issuance of the EETC pass-through trusts to fund any Boeing 737 MAX deliveries.
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 and landing slots at certain airports and certain other assets. 6% Senior Notes due 2020 4.25% Senior Notes due 2022 5% Senior Notes due 2024 4.875% Senior Notes due 2025 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 programs.

Leases and Capacity Purchase _2

Leases and Capacity Purchase Agreements (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Components of Lease Cost	The Company's lease cost for the years ended December 31 included the following components (in millions): 2019 2018 2017 Operating lease cost $ 1,038 $ 1,213 $ 1,433 Variable and short-term lease cost 2,548 2,569 2,209 Amortization of finance lease assets 68 75 77 Interest on finance lease liabilities 85 44 24 Sublease income (32 ) (38 ) (36 ) Total lease cost $ 3,707 $ 3,863 $ 3,707
Summary of Scheduled Future Minimum Lease Payments under Operating Leases	The table below summarizes the Company's scheduled future minimum lease payments under operating and finance leases, recorded on the balance sheet, as of December 31, 2019 (in millions): Operating Leases Finance Leases 2020 $ 920 $ 62 2021 754 75 2022 591 49 2023 633 38 2024 626 35 After 2024 4,214 57 Minimum lease payments 7,738 316 Imputed interest (2,106 ) (50 ) Present value of minimum lease payments 5,632 266 Less: current maturities of lease obligations (686 ) (46 ) Long-term lease obligations $ 4,946 $ 220
Summary of Scheduled Future Minimum Lease Payments under Finance Leases	The table below summarizes the Company's scheduled future minimum lease payments under operating and finance leases, recorded on the balance sheet, as of December 31, 2019 (in millions): Operating Leases Finance Leases 2020 $ 920 $ 62 2021 754 75 2022 591 49 2023 633 38 2024 626 35 After 2024 4,214 57 Minimum lease payments 7,738 316 Imputed interest (2,106 ) (50 ) Present value of minimum lease payments 5,632 266 Less: current maturities of lease obligations (686 ) (46 ) Long-term lease obligations $ 4,946 $ 220
Additional Information Related to Leases	The table below presents additional information related to our leases as of December 31: 2019 2018 Weighted-average remaining lease term - operating leases 11 years 10 years Weighted-average remaining lease term - finance leases 6 years 5 years Weighted-average discount rate - operating leases 5.2 % 5.2 % Weighted-average discount rate - finance leases 5.7 % 45.8 %
Supplemental Cash Flow Information Related to Leases	The table below presents supplemental cash flow information related to leases during the year ended December 31 (in millions): 2019 2018 2017 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 902 $ 1,078 $ 1,451 Operating cash flows for finance leases 70 53 24 Financing cash flows for finance leases 151 79 84
Future Lease Payment Under Terms of Capacity Purchase Agreement	Based on these assumptions as of December 31, 2019 , our future payments through the end of the terms of our CPAs are presented in the table below (in billions): 2020 $ 2.9 2021 2.9 2022 2.4 2023 1.5 2024 1.3 After 2024 4.7 $ 15.7

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Summary of Commitments to Purchase Aircraft	As of December 31, 2019 , United had firm commitments and options to purchase aircraft from The Boeing Company ("Boeing"), Airbus S.A.S. ("Airbus") and Embraer S.A. ("Embraer") presented in the table below: Scheduled Aircraft Deliveries Aircraft Type Number of Firm 2020 After 2020 Airbus A321XLR 50 — 50 Airbus A350 45 — 45 Boeing 737 MAX 171 44 127 Boeing 777-300ER 2 2 — Boeing 787 16 15 1 Embraer E175 20 20 — (a) United also has options and purchase rights for additional aircraft. The table below summarizes United's commitments as of December 31, 2019 , which include aircraft and related spare engines, aircraft improvements and all non-aircraft capital commitments (in billions): 2020 $ 6.9 2021 4.3 2022 2.0 2023 1.0 2024 1.2 After 2024 11.3 $ 26.7

Special Charges and Unrealize_2

Special Charges and Unrealized (Gains) Losses on Investments (Tables)	12 Months Ended
	Dec. 31, 2019
Restructuring and Related Activities [Abstract]
Components of Special Charges	Special charges and unrealized gains and losses on investments in the statements of consolidated operations consisted of the following for the years ended December 31 (in millions): Operating: 2019 2018 2017 Impairment of assets $ 171 $ 377 $ 25 Severance and benefit costs 16 41 116 Termination of an engine maintenance service agreement — 64 — (Gains) losses on sale of assets and other special charges 59 5 35 Total operating special charges 246 487 176 Nonoperating unrealized (gains) losses on investments (153 ) 5 — Total special charges and unrealized (gains) losses on investments 93 492 176 Income tax benefit (21 ) (110 ) (63 ) Income tax adjustments (Note 6) — (5 ) (189 ) Total special charges and unrealized (gains) losses on investments, net of income taxes and income tax adjustments $ 72 $ 377 $ (76 )

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Summary of Selected Quarterly Financial Data	Quarter Ended (In millions, except per share amounts) March 31 June 30 September 30 December 31 2019 Operating revenue $ 9,589 $ 11,402 $ 11,380 $ 10,888 Income from operations 495 1,472 1,473 861 Net income 292 1,052 1,024 641 Basic earnings per share 1.09 4.03 4.01 2.54 Diluted earnings per share 1.09 4.02 3.99 2.53 2018 Operating revenue $ 9,032 $ 10,777 $ 11,003 $ 10,491 Income from operations (a) 262 1,145 1,187 635 Net income (a) 145 683 833 461 Basic earnings per share (a) 0.51 2.48 3.06 1.70 Diluted earnings per share (a) 0.51 2.48 3.05 1.69 (a) Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 of this report for additional information on the adjustments.
Impact of Significant Items on Quarterly Results	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 2019 Impairment of assets 8 61 — 102 Severance and benefit costs 6 6 2 2 (Gains) losses on sale of assets and other special charges 4 4 25 26 Total operating special charges 18 71 27 130 Nonoperating unrealized (gains) losses on investments (17 ) (34 ) (21 ) (81 ) Total special charges and unrealized (gains) losses on investments 1 37 6 49 Income tax benefit related to special charges and unrealized (gains) losses on investments — (8 ) (2 ) (11 ) Total special charges and unrealized (gains) losses on investments, net of income tax 1 29 4 38 2018 Impairment of assets $ 23 $ 111 $ 11 $ 232 Termination of an engine maintenance service agreement — — — 64 Severance and benefit costs 14 11 9 7 (Gains) losses on sale of assets and other special charges 3 7 (3 ) (2 ) Total operating special charges 40 129 17 301 Nonoperating unrealized (gains) losses on investments (45 ) 135 (29 ) (56 ) Total special charges and unrealized (gains) losses on investments (5 ) 264 (12 ) 245 Income tax benefit related to special charges and unrealized (gains) losses on investments 1 (59 ) 3 (55 ) Income tax adjustments — — — (5 ) Total special charges and unrealized (gains) losses on investments, net of income tax $ (4 ) $ 205 $ (9 ) $ 185

Significant Accounting Polici_4

Significant Accounting Policies - Operating Revenue by Principal Geographic Region (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 10,888	$ 11,380	$ 11,402	$ 9,589	$ 10,491	$ 11,003	$ 10,777	$ 9,032	$ 43,259	$ 41,303	[1]	$ 37,784	[1]
Domestic (U.S. and Canada)
Disaggregation of Revenue [Line Items]
Revenue									26,960	25,552		23,114
Atlantic
Disaggregation of Revenue [Line Items]
Revenue									7,387	7,103		6,340
Pacific
Disaggregation of Revenue [Line Items]
Revenue									5,132	5,188		4,914
Latin America
Disaggregation of Revenue [Line Items]
Revenue									$ 3,780	$ 3,460		$ 3,416
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Significant Accounting Polici_5

Significant Accounting Policies - Narrative (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Summary Of Significant Accounting Policies [Line Items]
Period over which miles are expected to be redeemed									P2Y
Revenue	$ 10,888	$ 11,380	$ 11,402	$ 9,589	$ 10,491	$ 11,003	$ 10,777	$ 9,032	$ 43,259	$ 41,303	[1]	$ 37,784	[1]
Carrying value of computer software	422				$ 359				422	359
Amortization expense									60	67		79
Projected amortization expense in 2020	55								55
Projected amortization expense in 2021	50								50
Projected amortization expense in 2022	40								40
Projected amortization expense in 2023	37								37
Projected amortization expense in 2024	$ 32								32
Advertising expense									$ 212	211		217
Minimum
Summary Of Significant Accounting Policies [Line Items]
Frequent flier program expiration period									1 year
Maximum
Summary Of Significant Accounting Policies [Line Items]
Frequent flier program expiration period									9 years
Computer software
Summary Of Significant Accounting Policies [Line Items]
Depreciation expense									$ 135	122		117
Advance Ticket Sales
Summary Of Significant Accounting Policies [Line Items]
Passenger revenue included in advance ticket sales recognized									3,400	3,100
Ancillary Fees Recorded within Passenger Revenues
Summary Of Significant Accounting Policies [Line Items]
Revenue									2,400	2,200		2,000
Other Operating Revenue
Summary Of Significant Accounting Policies [Line Items]
Revenue									2,455	2,360	[1]	2,210	[1]
Other Operating Revenue | Chase and Other Partner Agreements
Summary Of Significant Accounting Policies [Line Items]
Revenue									$ 2,000	2,000		$ 1,800
One-time payment										$ 50
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Significant Accounting Polici_6

Significant Accounting Policies - Roll Forward of Frequent Flier Deferred Revenue (Details) - Frequent Flyer - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Movement in Deferred Revenue [Roll Forward]
Total Frequent flyer deferred revenue - beginning balance	$ 5,005	$ 4,783
Total miles awarded	2,621	2,451
Travel miles redeemed (Passenger revenue)	(2,213)	(2,068)
Non-travel miles redeemed (Other operating revenue)	(137)	(161)
Total Frequent flyer deferred revenue - ending balance	$ 5,276	$ 5,005

Significant Accounting Polici_7

Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 2,762	$ 1,694	[1]	$ 1,482
Other assets:
Restricted cash	106	105	[1]	91
Total cash, cash equivalents and restricted cash shown in the statement of consolidated cash flows	2,868	1,799	[2]	1,591	[2]	$ 2,303	[2]
Prepaid Expenses and Other
Current assets:
Restricted cash	0	0		18
United Airlines, Inc.
Current assets:
Cash and cash equivalents	2,756	1,688	[3]	1,476
Other assets:
Restricted cash	106	105	[3]	91
Total cash, cash equivalents and restricted cash shown in the statement of consolidated cash flows	2,862	1,793	[4]	1,585	[4]	$ 2,297	[4]
United Airlines, Inc. | Prepaid Expenses and Other
Current assets:
Restricted cash	$ 0	$ 0		$ 18
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[2]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[3]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[4]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Significant Accounting Polici_8

Significant Accounting Policies - Estimated Useful Lives of Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2019
Aircraft, spare engines and related rotable parts | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	25 years
Aircraft, spare engines and related rotable parts | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	30 years
Aircraft seats | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Aircraft seats | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	15 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

Significant Accounting Polici_9

Significant Accounting Policies - Information about Goodwill and Other Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Goodwill	$ 4,523	$ 4,523	[1]
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	2,693	2,783
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,756	1,756
Accumulated Amortization	1,440	1,380	[1]
Route authorities
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	1,150	1,240
Airport slots and gates
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	546	546
Tradenames and logos
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	593	593
Alliances
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	404	404
Frequent flyer database
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,177	1,177
Accumulated Amortization	931	884
Hubs
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	145	145
Accumulated Amortization	104	97
Contracts
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	120	120
Accumulated Amortization	111	106
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	314	314
Accumulated Amortization	$ 294	$ 293
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Significant Accounting Polic_10

Significant Accounting Policies - Impact of the Adoption of the New Lease Standard (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018		Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Statements of Consolidated Operations
Regional capacity purchase										$ 2,849	$ 2,649	[1]	$ 2,268	[1]
Landing fees and other rent										2,543	2,449	[1]	2,310	[1]
Depreciation and amortization										2,288	2,165	[1],[2]	2,096	[1],[2]
Interest expense											(670)		(626)
Interest capitalized										85	65	[1]	74	[1]
Income tax expense										905	526	[1]	880	[1]
Net income	$ 641	$ 1,024	$ 1,052	$ 292	$ 461		$ 833	$ 683	$ 145	$ 3,009	$ 2,122	[1],[2],[3],[4]	$ 2,143	[1],[2],[3],[4]
Earnings per share, basic (in dollars per share)	$ 2.54	$ 4.01	$ 4.03	$ 1.09	$ 1.70		$ 3.06	$ 2.48	$ 0.51	$ 11.63	$ 7.70	[1]	$ 7.08	[1]
Earnings per share, diluted (in dollars per share)	$ 2.53	$ 3.99	$ 4.02	$ 1.09	$ 1.69		$ 3.05	$ 2.48	$ 0.51	$ 11.58	$ 7.67	[1]	$ 7.06	[1]
Consolidated Balance Sheets
Receivables, less allowance for doubtful accounts	$ 1,364				$ 1,426	[5]				$ 1,364	$ 1,426	[5]
Prepaid expenses and other	814				733	[5]				814	733	[5]
Flight equipment, owned and finance leases					32,599						32,599
Other property and equipment, owned and finance leases	7,926				6,889	[5]				7,926	6,889	[5]
Accumulated depreciation and amortization, owned and finance leases					(13,266)						(13,266)
Operating lease right-of-use assets	4,758				5,262	[5]				4,758	5,262	[5]
Current maturities of finance leases	46				123	[5]				46	123	[5]
Current maturities of operating leases	686				719	[5]				686	719	[5]
Other current liabilities	566				553	[5]				566	553	[5]
Long-term obligations under finance leases	220				224	[5]				220	224	[5]
Long-term obligations under operating leases	4,946				5,276	[5]				4,946	5,276	[5]
Deferred income taxes	1,736				828	[5]				1,736	828	[5]
Other long-term liabilities	1,024				1,010	[5]				1,024	1,010	[5]
Retained earnings	$ 9,716				6,715	[5]				9,716	6,715	[5]
Cash Flows from Operating Activities:
Net cash provided by operating activities										6,909	6,164	[2]	$ 3,474	[2]
Cash Flows from Investing Activities:
Capital expenditures										(4,528)	(4,070)	[2]	(3,870)	[2]
Cash Flows from Financing Activities:
Proceeds from issuance of long-term debt										1,847	1,594	[2]	2,537	[2]
Principal payments under finance leases										$ (151)	(79)	[2]	(84)	[2]
As Reported
Statements of Consolidated Operations
Regional capacity purchase											2,601		2,232
Landing fees and other rent											2,359		2,240
Depreciation and amortization											2,240		2,149
Interest expense											(729)		(671)
Interest capitalized											70		84
Income tax expense											529		896
Net income											$ 2,129		$ 2,144
Earnings per share, basic (in dollars per share)											$ 7.73		$ 7.08
Earnings per share, diluted (in dollars per share)											$ 7.70		$ 7.06
Consolidated Balance Sheets
Receivables, less allowance for doubtful accounts					1,346						$ 1,346
Prepaid expenses and other					913						913
Flight equipment, owned and finance leases					32,636						32,636
Other property and equipment, owned and finance leases					7,930						7,930
Accumulated depreciation and amortization, owned and finance leases					(13,414)						(13,414)
Operating lease right-of-use assets					0						0
Current maturities of finance leases					149						149
Current maturities of operating leases					0						0
Other current liabilities					619						619
Long-term obligations under finance leases					1,134						1,134
Long-term obligations under operating leases					0						0
Deferred income taxes					814						814
Other long-term liabilities					1,832						1,832
Retained earnings					6,668						6,668
Cash Flows from Operating Activities:
Net cash provided by operating activities											6,181		$ 3,413
Cash Flows from Investing Activities:
Capital expenditures											(4,177)		(3,998)
Cash Flows from Financing Activities:
Proceeds from issuance of long-term debt											1,740		2,765
Principal payments under finance leases											(134)		(124)
ASU 2016-02 | New Lease Standard Adjustments
Statements of Consolidated Operations
Regional capacity purchase											48		36
Landing fees and other rent											90		70
Depreciation and amortization											(75)		(53)
Interest expense											59		45
Interest capitalized											(5)		(10)
Income tax expense											(3)		(16)
Net income											$ (7)		$ (1)
Earnings per share, basic (in dollars per share)											$ (0.03)		$ 0
Earnings per share, diluted (in dollars per share)											$ (0.03)		$ 0
Consolidated Balance Sheets
Receivables, less allowance for doubtful accounts					80						$ 80
Prepaid expenses and other					(180)						(180)
Flight equipment, owned and finance leases					(37)						(37)
Other property and equipment, owned and finance leases					(1,041)						(1,041)
Accumulated depreciation and amortization, owned and finance leases					148						148
Operating lease right-of-use assets					5,262						5,262
Current maturities of finance leases					(26)						(26)
Current maturities of operating leases					719						719
Other current liabilities					(66)						(66)
Long-term obligations under finance leases					(910)						(910)
Long-term obligations under operating leases					5,276						5,276
Deferred income taxes					14						14
Other long-term liabilities					(822)						(822)
Retained earnings					$ 47						47
Cash Flows from Operating Activities:
Net cash provided by operating activities											(17)		$ 61
Cash Flows from Investing Activities:
Capital expenditures											107		128
Cash Flows from Financing Activities:
Proceeds from issuance of long-term debt											(146)		(228)
Principal payments under finance leases											$ 55		$ 40
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[2]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[3]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8
[4]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[5]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Common Stockholders' Equity a_2

Common Stockholders' Equity and Preferred Securities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jul. 31, 2019
Equity [Abstract]
Number of shares repurchased (in shares)	19,200,000
Repurchases of common stock	$ 1,641,000,000	$ 1,250,000,000	$ 1,844,000,000
Authorized amount under share repurchase program			$ 3,000,000,000	$ 3,000,000,000
Amount remaining under repurchase programs	$ 3,100,000,000
Common stock reserved for future issuance (in shares)	8,000,000
Junior preferred stock outstanding (in shares)	2
Junior preferred stock par value per share (in dollars per share)	$ 0.01
Preferred stock authorized to issue (in shares)	250,000,000

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings available to common stockholders									$ 3,009	$ 2,122		$ 2,143
Basic weighted-average shares outstanding (in shares)									258.8	275.5		302.7
Effect of employee stock awards (in shares)									1.1	1.2		0.9
Diluted weighted-average shares outstanding (in shares)									259.9	276.7		303.6
Earnings per share, basic (in dollars per share)	$ 2.54	$ 4.01	$ 4.03	$ 1.09	$ 1.70	$ 3.06	$ 2.48	$ 0.51	$ 11.63	$ 7.70	[1]	$ 7.08	[1]
Earnings per share, diluted (in dollars per share)	$ 2.53	$ 3.99	$ 4.02	$ 1.09	$ 1.69	$ 3.05	$ 2.48	$ 0.51	$ 11.58	$ 7.67	[1]	$ 7.06	[1]
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Share-Based Compensation Plan_2

Share-Based Compensation Plans - Narrative (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of RSUs and restricted stock vested in period	$ 99	$ 70	$ 76
Stock option awards outstanding (in shares)	700
Stock option awards exercisable (in shares)	200
Weighted-average exercise price of stock options outstanding (in dollars per share)	$ 82.12
Weighted-average exercise price of stock options exercisable (in dollars per share)	$ 56.89
Intrinsic value of stock options outstanding	$ 11
Intrinsic value of stock options exercisable	$ 6
Weighted average remaining contractual lives of stock options outstanding	7 years 3 months 18 days
Weighted average remaining contractual lives of stock options exercisable	3 years 8 months 12 days
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)	1,200
Number of days used to compute performance period average closing price of restricted stock units	20 days
Liabilities related to share based payments	$ 44
Payment related to share-based liabilities	$ 41	$ 28	$ 50
Time-Vested RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)	900
Vesting period	3 years
Performance-Based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)	300
Vesting period	3 years
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	6 years
Award term	10 years
Stock options granted (in shares)	307		36
Percentage of premium of the grant date fair market value	25.00%
Weighted-average grant date exercise price of stock options granted (in dollars per share)	$ 110.21		$ 77.56
Weighted-average grant date fair value of stock options granted			$ 0.7

Share-Based Compensation Plan_3

Share-Based Compensation Plans - Information Related to Share-Based Compensation Plan Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	$ 100	$ 101	$ 73
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	98	98	63
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	1	2	8
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	$ 1	$ 1	$ 2

Share-Based Compensation Plan_4

Share-Based Compensation Plans - Summary of Unearned Compensation and Weighted-Average Remaining Period to Recognize Costs (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unearned compensation	$ 77
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unearned compensation	$ 66
Weighted average remaining period	2 years
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unearned compensation	$ 11
Weighted average remaining period	5 years 3 months 18 days

Share-Based Compensation Plan_5

Share-Based Compensation Plans - Summary of RSU and Restricted Stock Activity (Details) - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Liability Awards - RSUs
Awards
Outstanding (in shares)	1.9	1.8	2.1
Granted (in shares)	0.1	0.7	0.6
Vested (in shares)	(0.5)	(0.5)	(0.7)
Forfeited (in shares)	(0.9)	(0.1)	(0.2)
Outstanding (in shares)	0.6	1.9	1.8
Equity Awards - RSUs
Awards
Outstanding (in shares)	1.8	1.4	0.8
Granted (in shares)	1.1	1.1	1
Vested (in shares)	(0.8)	(0.5)	(0.3)
Forfeited (in shares)	(0.1)	(0.2)	(0.1)
Outstanding (in shares)	2	1.8	1.4
Weighted- Average Grant Price
Outstanding (in dollars per share)	$ 66.29	$ 63.99	$ 51.67
Granted (in dollars per share)	86.72	67.74	71.68
Vested (in dollars per share)	64.85	63.02	51.81
Forfeited (in dollars per share)	76.48	67.34	57.49
Outstanding (in dollars per share)	$ 78.03	$ 66.29	$ 63.99
Restricted Stock
Awards
Outstanding (in shares)	0.1	0.3	0.5
Granted (in shares)	0	0	0
Vested (in shares)	(0.1)	(0.2)	(0.2)
Forfeited (in shares)	0	0	0
Outstanding (in shares)	0	0.1	0.3
Weighted- Average Grant Price
Outstanding (in dollars per share)	$ 51.17	$ 52.30	$ 52
Granted (in dollars per share)	0	0	0
Vested (in dollars per share)	51.17	53.24	51.60
Forfeited (in dollars per share)	0	0	0
Outstanding (in dollars per share)	$ 0	$ 51.17	$ 52.30

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) - Components of the Company's AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, deferred taxes	$ (136)		$ (39)		$ 26
Balance	10,042	[1]	8,788		8,574
Change in value, deferred tax	(24)		(83)		74
Change in value	88		289		(239)
Amounts reclassified to earnings, deferred taxes	0		13		21
Amounts reclassified to earnings	(3)		49		39
Reclassification of stranded tax effects					0
Amounts reclassified to retained earnings, deferred taxes			(1)
Amounts reclassified to retained earnings			6
Balance, deferred taxes	(160)		(136)		(39)
Balance	11,531		10,042	[1]	8,788
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(803)		(1,147)		(829)
Reclassification of stranded tax effects					(118)
Balance	(718)		(803)		(1,147)
Pension and Other Postretirement Liabilities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, before tax	(663)		(1,102)		(854)
Change in value, before tax	105		377		(306)
Amounts reclassified to earnings, before tax	(2)		62		58
Amounts reclassified to retained earnings, before tax			0
Balance, before tax	(560)		(663)		(1,102)
Investments and Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, before tax	(4)		(6)		(1)
Change in value, before tax	7		(5)		(7)
Amounts reclassified to earnings, before tax	(1)		0		2
Amounts reclassified to retained earnings, before tax			7
Balance, before tax	$ 2		$ (4)		$ (6)
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Income Taxes - Income Tax Provi

Income Taxes - Income Tax Provision (Benefit) Differed from Amounts Computed at the Statutory Federal Income Tax Rate and Significant Components (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Income Taxes [Line Items]
Income tax provision at statutory rate	$ 822	$ 556		$ 1,058
State income taxes, net of federal income tax benefit	50	29		30
Foreign tax rate differential	(90)	(84)		(43)
Global intangible low-taxed income	90	4		0
Foreign income taxes	1	2		3
Nondeductible employee meals	12	12		17
Impact of Tax Act	0	(5)		(189)
State rate change	0	3		12
Valuation allowance	(4)	(3)		(16)
Other, net	24	12		8
Income tax expense (benefit)	905	526	[1]	880	[1]
Current	23	14		(77)
Deferred	882	512	[2]	957	[2]
Valuation allowance recorded	58	59
United Airlines, Inc.
Income Taxes [Line Items]
Income tax provision at statutory rate	822	557		1,059
State income taxes, net of federal income tax benefit	50	29		30
Foreign tax rate differential	(90)	(84)		(43)
Global intangible low-taxed income	90	4		0
Foreign income taxes	1	2		3
Nondeductible employee meals	12	12		17
Impact of Tax Act	0	(5)		(206)
State rate change	0	3		12
Valuation allowance	(4)	(3)		(16)
Other, net	24	12		8
Income tax expense (benefit)	905	527	[3]	864	[3]
Current	23	14		(77)
Deferred	882	513	[4]	$ 941	[4]
Valuation allowance recorded	$ 58	$ 59
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[2]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[3]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[4]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
NOLs without an expiration date	$ 1,300
Unrecognized tax benefits	53	$ 39	$ 21
Unrecognized tax benefits that would impact effective tax rate if recognized	53
2030
Income Taxes [Line Items]
NOL carry forwards	700
2033
Income Taxes [Line Items]
NOL carry forwards	500
Thereafter
Income Taxes [Line Items]
NOL carry forwards	500
Federal
Income Taxes [Line Items]
NOL carry forwards	3,000
State
Income Taxes [Line Items]
NOL carry forwards	100
NOL carry forwards, valuation allowance	$ 45
State | Minimum
Income Taxes [Line Items]
NOL expiration period	5 years
State | Maximum
Income Taxes [Line Items]
NOL expiration period	20 years

Income Taxes - Temporary Differ

Income Taxes - Temporary Differences and Carryforwards Giving Rise to Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred income tax asset (liability):
Federal and state net operating loss (NOL) carryforwards	$ 695	$ 398
Deferred revenue	1,287	1,232
Employee benefits, including pension, postretirement and medical	715	885
Operating lease liabilities	1,256	1,338
Other	165	229
Less: Valuation allowance	(58)	(59)
Total deferred tax assets	4,060	4,023
Depreciation	(4,011)	(2,929)
Operating lease right-of-use asset	(1,061)	(1,173)
Intangibles	(724)	(749)
Total deferred tax liabilities	(5,796)	(4,851)
Net deferred tax liability	(1,736)	(828)
United Airlines, Inc.
Deferred income tax asset (liability):
Federal and state net operating loss (NOL) carryforwards	668	371
Deferred revenue	1,287	1,232
Employee benefits, including pension, postretirement and medical	715	885
Operating lease liabilities	1,256	1,338
Other	165	229
Less: Valuation allowance	(58)	(59)
Total deferred tax assets	4,033	3,996
Depreciation	(4,011)	(2,929)
Operating lease right-of-use asset	(1,061)	(1,173)
Intangibles	(724)	(749)
Total deferred tax liabilities	(5,796)	(4,851)
Net deferred tax liability	$ (1,763)	$ (855)

Pension and Other Postretirem_3

Pension and Other Postretirement Plans - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Profit sharing and payroll tax expense	$ 491	$ 334	$ 349
Minimum
Defined Benefit Plan Disclosure [Line Items]
Percentage of pre-tax earnings paid for profit sharing plan	5.00%
Maximum
Defined Benefit Plan Disclosure [Line Items]
Percentage of pre-tax earnings paid for profit sharing plan	20.00%
IAM National Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Multi-employer plan contributions		$ 467
Percent of company's contribution to plan		5.00%
United Airlines, Inc.
Defined Benefit Plan Disclosure [Line Items]
Expense for defined contribution plans	$ 735	$ 693	$ 656
United Airlines, Inc. | Minimum
Defined Benefit Plan Disclosure [Line Items]
Employer contribution percentage	1.00%
United Airlines, Inc. | Maximum
Defined Benefit Plan Disclosure [Line Items]
Employer contribution percentage	16.00%
Retiree Medical Benefit Program
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.39%
Decrease in projected benefit obligation due to plan amendment and remeasurement	$ 421
Accumulated other comprehensive loss prior service	597
Actuarial loss net periodic benefit cost	$ 176
Participants in retiree medical benefit program, year	7 years
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.52%	4.20%
Increase in pension benefit liability if there was a 50 basis point decrease in the weighted average discount rate	$ 700
Increase in benefits expense if there was a 50 basis point decrease in the weighted average discount rate	69
Decrease in expected long-term rate of return on plan assets if there was a 50 basis point decrease in the weighted average discount rate	20
Expected employer contributions to pension and postretirement plans	$ 314
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.35%	4.30%
Increase in pension benefit liability if there was a 50 basis point decrease in the weighted average discount rate	$ 42
Increase in benefits expense if there was a 50 basis point decrease in the weighted average discount rate	4
Expected employer contributions to pension and postretirement plans	$ 47
Other Postretirement Benefits | Deposit Administration Fund
Defined Benefit Plan Disclosure [Line Items]
Percent of plan assets invested	100.00%

Pension and Other Postretirem_4

Pension and Other Postretirement Plans - Reconciliation of the Change in Benefit Obligation and Plan Asset, Funded Status and Amounts Recognized in the Financial Statements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in projected benefit obligation:
Plan amendments	$ (597)	$ 0
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	5,333	4,448
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	5,396	5,852
Service cost	184	228	$ 195
Interest cost	226	217	220
Actuarial (gain) loss	784	(601)
Gross benefits paid and settlements	(200)	(292)
Other	8	(8)
Projected benefit obligation at end of year	6,398	5,396	5,852
Change in plan assets:
Fair value of plan assets at beginning of year	3,827	3,932
Actual (loss) return on plan assets	684	(215)
Employer contributions	649	413
Gross benefits paid and settlements	(200)	(292)
Other	4	(11)
Fair value of plan assets at end of year	4,964	3,827	3,932
Funded status—Net amount recognized	(1,434)	(1,569)
Amounts recognized in the consolidated balance sheets consist of:
Noncurrent asset	14	13
Current liability	(2)	(6)
Noncurrent liability	(1,446)	(1,576)
Total liability	(1,434)	(1,569)
Amounts recognized in accumulated other comprehensive loss consist of:
Net actuarial loss	(1,652)	(1,382)
Prior service cost	(4)	(5)
Total accumulated other comprehensive loss	(1,656)	(1,387)
Other Postretirement Benefits
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	1,391	1,710
Service cost	10	12	13
Interest cost	47	61	66
Plan participants' contributions	67	68
Benefits paid	(180)	(181)
Actuarial (gain) loss	99	(285)
Other	5	6
Projected benefit obligation at end of year	842	1,391	1,710
Change in plan assets:
Fair value of plan assets at beginning of year	53	54
Actual (loss) return on plan assets	1	1
Employer contributions	111	111
Plan participants' contributions	67	68
Benefits paid	(180)	(181)
Fair value of plan assets at end of year	52	53	$ 54
Funded status—Net amount recognized	(790)	(1,338)
Amounts recognized in the consolidated balance sheets consist of:
Current liability	(1)	(43)
Noncurrent liability	(789)	(1,295)
Total liability	(790)	(1,338)
Amounts recognized in accumulated other comprehensive loss consist of:
Net actuarial loss	403	554
Prior service cost	693	170
Total accumulated other comprehensive loss	$ 1,096	$ 724

Pension and Other Postretirem_5

Pension and Other Postretirement Plans - Accumulated Benefit Obligation and Projected Benefit Obligation in Excess of Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Projected benefit obligation	$ 6,161	$ 5,196
Accumulated benefit obligation	5,137	4,286
Fair value of plan assets	$ 4,714	$ 3,614

Pension and Other Postretirem_6

Pension and Other Postretirement Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 184	$ 228	$ 195
Interest cost	226	217	220
Expected return on plan assets	(291)	(292)	(243)
Amortization of unrecognized actuarial (gain) loss	118	130	128
Amortization of prior service credits	0	0	0
Other	5	1	5
Net periodic benefit cost (credit)	242	284	305
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	10	12	13
Interest cost	47	61	66
Expected return on plan assets	(1)	(2)	(2)
Amortization of unrecognized actuarial (gain) loss	(52)	(32)	(33)
Amortization of prior service credits	(73)	(37)	(37)
Other	0	0	0
Net periodic benefit cost (credit)	$ (69)	$ 2	$ 7

Pension and Other Postretirem_7

Pension and Other Postretirement Plans - Assumptions Used for Benefit Plans (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits
Assumptions used to determine benefit obligations
Discount rate	3.52%	4.20%
Rate of compensation increase	3.89%	3.89%
Assumptions used to determine net expense
Discount rate	4.21%	3.65%
Expected return on plan assets	7.40%	7.31%
Rate of compensation increase	3.89%	3.89%
Other Postretirement Benefits
Assumptions used to determine benefit obligations
Discount rate	3.35%	4.30%
Assumptions used to determine net expense
Discount rate	4.30%	3.63%
Expected return on plan assets	3.00%	3.00%
Health care cost trend rate assumed for next year	6.00%	6.00%
Rate to which the cost trend rate is assumed to decline (ultimate trend rate in 2033)	5.00%	5.00%

Pension and Other Postretirem_8

Pension and Other Postretirement Plans - Allocation of Plan Assets (Details) - United Airlines, Inc.	12 Months Ended
	Dec. 31, 2019
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return	10.00%
Equity securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Percent of total	30.00%
Equity securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Percent of total	45.00%
Fixed-income securities
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return	5.00%
Fixed-income securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Percent of total	35.00%
Fixed-income securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Percent of total	50.00%
Alternatives
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return	7.00%
Alternatives | Minimum
Defined Benefit Plan Disclosure [Line Items]
Percent of total	15.00%
Alternatives | Maximum
Defined Benefit Plan Disclosure [Line Items]
Percent of total	25.00%

Pension and Other Postretirem_9

Pension and Other Postretirement Plans - Pension and Other Postretirement Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Level 3
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	$ 409	$ 350	$ 383
Pension Benefits
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	4,964	3,827	3,932
Pension Benefits | Level 1
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	513	478
Pension Benefits | Level 2
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	825	751
Pension Benefits | Level 3
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	357	297
Pension Benefits | Assets Measured at NAV
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	3,269	2,301
Pension Benefits | Equity securities funds
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	1,957	1,457
Pension Benefits | Equity securities funds | Level 1
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	47	254
Pension Benefits | Equity securities funds | Level 2
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	117	106
Pension Benefits | Equity securities funds | Level 3
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	71	63
Pension Benefits | Equity securities funds | Assets Measured at NAV
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	1,722	1,034
Pension Benefits | Fixed-income securities
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	1,732	1,520
Pension Benefits | Fixed-income securities | Level 1
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Benefits | Fixed-income securities | Level 2
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	687	628
Pension Benefits | Fixed-income securities | Level 3
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	69	87
Pension Benefits | Fixed-income securities | Assets Measured at NAV
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	976	805
Pension Benefits | Alternatives
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	776	596
Pension Benefits | Alternatives | Level 1
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Benefits | Alternatives | Level 2
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Benefits | Alternatives | Level 3
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	205	134
Pension Benefits | Alternatives | Assets Measured at NAV
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	571	462
Pension Benefits | Other
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	499	254
Pension Benefits | Other | Level 1
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	466	224
Pension Benefits | Other | Level 2
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	21	17
Pension Benefits | Other | Level 3
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	12	13
Pension Benefits | Other | Assets Measured at NAV
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	52	53	$ 54
Other Postretirement Benefits | Deposit administration fund
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	52	53
Other Postretirement Benefits | Deposit administration fund | Level 1
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Deposit administration fund | Level 2
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefits | Deposit administration fund | Level 3
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	52	53
Other Postretirement Benefits | Deposit administration fund | Assets Measured at NAV
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0

Pension and Other Postretire_10

Pension and Other Postretirement Plans - Defined Benefit Plan Assets Measured at Fair Value Using Unobservable Inputs (Details) - Level 3 - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Fair value of plan assets at beginning of year	$ 350	$ 383
Actual return (loss) on plan assets:
Sold during the year	12	10
Held at year end	(1)	(21)
Purchases, sales, issuances and settlements (net)	48	(22)
Fair value of plan assets at end of year	$ 409	$ 350

Pension and Other Postretire_11

Pension and Other Postretirement Plans - Estimated Future Benefit Payments (Details) $ in Millions	Dec. 31, 2019USD ($)
Pension Benefits
Pension and Other Postretirement
2020	$ 361
2021	386
2022	399
2023	410
2024	399
Years 2025 – 2029	2,219
Other Postretirement Benefits
Pension and Other Postretirement
2020	53
2021	56
2022	59
2023	62
2024	64
Years 2025 – 2029	$ 328

Pension and Other Postretire_12

Pension and Other Postretirement Plans - Participation in the IAM National Pension Plan (Details) - IAM National Pension Plan - Multi-Employer Pension Plans - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Multiemployer Plans [Line Items]
Additional contribution rate	2.50%
Surcharge Imposed	No
United Airlines, Inc.
Multiemployer Plans [Line Items]
United's Contributions	$ 59	$ 52	$ 50

Notes Receivable (Details)

Notes Receivable (Details) $ / shares in Units, shares in Millions, adr in Millions	1 Months Ended
	Dec. 31, 2019USD ($)	Nov. 18, 2019USD ($)$ / shares	Nov. 30, 2018USD ($)adrshares
BRW | Term Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan amount			$ 456,000,000
Number of shares pledged as collateral (in shares) | shares			516
Implied value equivalent of shares pledged as collateral (in ADRs) | adr			64.5
Carrying amount of loan receivable	$ 499,000,000
AVH | Convertible Term Loan | United Airlines, Inc. and Kingsland International Group, S.A.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest rate	3.00%
Principal increments required for conversion		$ 5,000,000
Conversion price per one American Depository Share or eight AVH shares (in dollars per share) | $ / shares		$ 4.6217
Conversion price if a change of control occurs (in dollars per share) | $ / shares		$ 4.1595
Percent of outstanding principal amount required to be exercised if criteria is met		100.00%
AVH | Convertible Term Loan | United Airlines, Inc.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Issuance of notes receivable	$ 150,000,000

Investments and Fair Value Me_3

Investments and Fair Value Measurements - Fair Value of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Measured on a Recurring Basis - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 2,762	$ 1,694
Restricted cash	106	105
Equity securities	385	249
AVH Derivative Assets	24	11
Corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	1,045	1,023
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	690	746
U.S. government and agency notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	124	108
Certificates of deposit placed through an account registry service (CDARS)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	35	75
Other fixed-income securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	95	116
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	2,762	1,694
Restricted cash	106	105
Equity securities	385	249
AVH Derivative Assets	0	0
Level 1 | Corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 1 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 1 | U.S. government and agency notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 1 | Certificates of deposit placed through an account registry service (CDARS)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 1 | Other fixed-income securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Restricted cash	0	0
Equity securities	0	0
AVH Derivative Assets	0	0
Level 2 | Corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	1,045	1,023
Level 2 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	690	746
Level 2 | U.S. government and agency notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	124	108
Level 2 | Certificates of deposit placed through an account registry service (CDARS)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	35	75
Level 2 | Other fixed-income securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	95	116
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Restricted cash	0	0
Equity securities	0	0
AVH Derivative Assets	24	11
Level 3 | Corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 3 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 3 | U.S. government and agency notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 3 | Certificates of deposit placed through an account registry service (CDARS)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 3 | Other fixed-income securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
NAV | Other investments measured at NAV
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	$ 193	$ 188

Investments and Fair Value Me_4

Investments and Fair Value Measurements - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Fair Value [Line Items]
Investments in securities accounted for under the equity method	$ 126
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	15 years
Corporate Debt
Fair Value [Line Items]
Available-for-sale securities remaining maturities	3 years
CDARS
Fair Value [Line Items]
Available-for-sale securities remaining maturities	1 year
U.S. Government and Other Securities
Fair Value [Line Items]
Available-for-sale securities remaining maturities	3 years
Fixed Income Securities
Fair Value [Line Items]
Available-for-sale securities remaining maturities	2 years
Azul
Fair Value [Line Items]
Equity stake	2.00%
Carrying value of investment	$ 385
Azul | Preferred Stock
Fair Value [Line Items]
Equity stake	8.00%
Republic
Fair Value [Line Items]
Ownership stake	19.00%
ManaAir
Fair Value [Line Items]
Ownership stake	49.90%
Champlain
Fair Value [Line Items]
Ownership stake	40.00%
Fulcrum
Fair Value [Line Items]
Ownership interest	0.07
Carrying value of other investment	$ 51
Fulcrum | Preferred Stock
Fair Value [Line Items]
Ownership interest	0.08

Investments and Fair Value Me_5

Investments and Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, carrying amount	$ 14,552	$ 13,445
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	15,203	13,450
Fair Value | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Fair Value | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	11,398	9,525
Fair Value | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 3,805	$ 3,925

Debt - Summary of Long-Term Deb

Debt - Summary of Long-Term Debt (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Long term debt	$ 14,733	$ 13,636
Less: unamortized debt discount, premiums and debt issuance costs	(181)	(191)
Less: current portion of long-term debt	(1,407)	(1,230)	[1]
Long-term debt, net	$ 13,145	12,215	[1]
6% Senior Notes due 2020
Debt Instrument [Line Items]
Fixed interest rate	6.00%
4.25% Senior Notes due 2022
Debt Instrument [Line Items]
Fixed interest rate	4.25%
5% Senior Notes due 2024
Debt Instrument [Line Items]
Fixed interest rate	5.00%
4.875% Senior Notes due 2025
Debt Instrument [Line Items]
Fixed interest rate	4.25%
Secured Debt | Notes payable, fixed interest rates of 2.7% to 9.8% (weighted average rate of 3.95% as of December 31, 2019), payable through 2032
Debt Instrument [Line Items]
Long term debt	$ 9,615	8,811
Weighted average rate	3.95%
Secured Debt | Notes payable, fixed interest rates of 2.7% to 9.8% (weighted average rate of 3.95% as of December 31, 2019), payable through 2032 | Minimum
Debt Instrument [Line Items]
Fixed interest rate	2.70%
Secured Debt | Notes payable, fixed interest rates of 2.7% to 9.8% (weighted average rate of 3.95% as of December 31, 2019), payable through 2032 | Maximum
Debt Instrument [Line Items]
Fixed interest rate	9.80%
Secured Debt | Notes payable, floating interest rates of the London interbank offered rate (LIBOR) plus 1.05% to 2.25%, payable through 2030
Debt Instrument [Line Items]
Long term debt	$ 1,970	2,051
Secured Debt | Notes payable, floating interest rates of the London interbank offered rate (LIBOR) plus 1.05% to 2.25%, payable through 2030 | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	1.05%
Secured Debt | Notes payable, floating interest rates of the London interbank offered rate (LIBOR) plus 1.05% to 2.25%, payable through 2030 | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	2.25%
Secured Debt | Term loan, LIBOR plus 1.75%, or alternative rate based on certain market rates plus 0.75%, due 2024
Debt Instrument [Line Items]
Long term debt	$ 1,459	1,474
Secured Debt | Term loan, LIBOR plus 1.75%, or alternative rate based on certain market rates plus 0.75%, due 2024 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%
Secured Debt | Term loan, LIBOR plus 1.75%, or alternative rate based on certain market rates plus 0.75%, due 2024 | Alternative Rate Based on Certain Market Interest Rates
Debt Instrument [Line Items]
Basis spread on variable rate	0.75%
Unsecured Debt | 6% Senior Notes due 2020
Debt Instrument [Line Items]
Long term debt	$ 300	300
Fixed interest rate	6.00%
Unsecured Debt | 4.25% Senior Notes due 2022
Debt Instrument [Line Items]
Long term debt	$ 400	400
Fixed interest rate	4.25%
Unsecured Debt | 5% Senior Notes due 2024
Debt Instrument [Line Items]
Long term debt	$ 300	300
Fixed interest rate	5.00%
Unsecured Debt | 4.875% Senior Notes due 2025
Debt Instrument [Line Items]
Long term debt	$ 350	0
Fixed interest rate	4.875%
Unsecured Debt | Other
Debt Instrument [Line Items]
Long term debt	$ 339	$ 300
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Debt - Contractual Principal Pa

Debt - Contractual Principal Payments under Outstanding Long-Term Debt Agreements (Details) - UAL and United $ in Millions	Dec. 31, 2019USD ($)
Debt Instrument [Line Items]
2020	$ 1,407
2021	1,415
2022	1,765
2023	815
2024	3,122
After 2024	6,209
Long-term debt	$ 14,733

Debt - Narrative (Details)

Debt - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	May 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Long term debt	$ 14,733,000,000		$ 13,636,000,000
Pass-Through Certificates
Debt Instrument [Line Items]
Long term debt	$ 9,600,000,000
4.875% Senior Notes due 2025
Debt Instrument [Line Items]
Fixed interest rate	4.25%
Line of Credit | Term Loan
Debt Instrument [Line Items]
Aggregate principal amount	$ 1,500,000,000
Quarterly principal repayment amount	0.25%
Line of Credit | Term Loan | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%
Line of Credit | Term Loan | Alternative Rate Based on Certain Market Interest Rates
Debt Instrument [Line Items]
Basis spread on variable rate	0.75%
Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Credit agreement	$ 2,000,000,000
Available under revolving credit facility	$ 2,000,000,000
Commitment fee percentage	0.75%
Line of Credit | Revolving Credit Facility | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	2.25%
Line of Credit | Revolving Credit Facility | Alternative Rate Based on Certain Market Interest Rates
Debt Instrument [Line Items]
Basis spread on variable rate	1.25%
Secured Debt | Borrowings Financing Aircraft Purchases
Debt Instrument [Line Items]
Aggregate principal amount	$ 105,000,000
Secured Debt | Special Facility Revenue Bonds
Debt Instrument [Line Items]
Aggregate principal amount	$ 295,000,000
Fixed interest rate	4.00%
Mortgage | Special Facility Revenue Bonds
Debt Instrument [Line Items]
Long term debt	$ 39,000,000
Senior Notes | 4.875% Senior Notes due 2025
Debt Instrument [Line Items]
Aggregate principal amount		$ 350,000,000
Fixed interest rate		4.875%

Debt - Details of Pass Through

Debt - Details of Pass Through Trusts (Details)	12 Months Ended
	Dec. 31, 2019USD ($)aircraft	Dec. 31, 2018USD ($)		Dec. 31, 2017USD ($)	[1]
Debt Instrument [Line Items]
Total debt recorded	$ 14,733,000,000	$ 13,636,000,000
Proceeds received from issuance of debt	$ 1,847,000,000	$ 1,594,000,000	[1]	$ 2,537,000,000
Boeing 737 MAX
Debt Instrument [Line Items]
Number of aircraft expected to take delivery of | aircraft	3
Pass-Through Certificates
Debt Instrument [Line Items]
Principal	$ 2,234,000,000
Total debt recorded	1,813,000,000
Proceeds received from issuance of debt	1,813,000,000
Amounts returned to holders of pass through certificates	93,000,000
Remaining proceeds from issuance of debt to be received in future periods	328,000,000
Class AA Pass Through Certificates Issued September 2019 | Pass-Through Certificates
Debt Instrument [Line Items]
Principal	$ 702,000,000
Stated interest rate	2.70%
Total debt recorded	$ 513,000,000
Proceeds received from issuance of debt	513,000,000
Amounts returned to holders of pass through certificates	0
Remaining proceeds from issuance of debt to be received in future periods	189,000,000
Class A Pass Through Certificates Issued September 2019 | Pass-Through Certificates
Debt Instrument [Line Items]
Principal	$ 287,000,000
Stated interest rate	2.90%
Total debt recorded	$ 210,000,000
Proceeds received from issuance of debt	210,000,000
Amounts returned to holders of pass through certificates	0
Remaining proceeds from issuance of debt to be received in future periods	77,000,000
Class B Pass Through Certificates Issued September 2019 | Pass-Through Certificates
Debt Instrument [Line Items]
Principal	$ 232,000,000
Stated interest rate	3.50%
Total debt recorded	$ 170,000,000
Proceeds received from issuance of debt	170,000,000
Amounts returned to holders of pass through certificates	0
Remaining proceeds from issuance of debt to be received in future periods	62,000,000
Class AA Pass Through Certificates Issued February 2019 | Pass-Through Certificates
Debt Instrument [Line Items]
Principal	$ 717,000,000
Stated interest rate	4.15%
Total debt recorded	$ 651,000,000
Proceeds received from issuance of debt	651,000,000
Amounts returned to holders of pass through certificates	66,000,000
Remaining proceeds from issuance of debt to be received in future periods	0
Class A Pass Through Certificates Issued February 2019 | Pass-Through Certificates
Debt Instrument [Line Items]
Principal	$ 296,000,000
Stated interest rate	4.55%
Total debt recorded	$ 269,000,000
Proceeds received from issuance of debt	269,000,000
Amounts returned to holders of pass through certificates	27,000,000
Remaining proceeds from issuance of debt to be received in future periods	$ 0
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Debt - Summary of Collateral Co

Debt - Summary of Collateral Covenants and Cross Default Provisions (Details) $ in Billions	Dec. 31, 2019USD ($)
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% Senior Notes due 2020
Debt Instrument [Line Items]
Fixed interest rate	6.00%
5% Senior Notes due 2024
Debt Instrument [Line Items]
Fixed interest rate	5.00%
4.25% Senior Notes due 2022
Debt Instrument [Line Items]
Fixed interest rate	4.25%
4.875% Senior Notes due 2025
Debt Instrument [Line Items]
Fixed interest rate	4.25%

Leases and Capacity Purchase _3

Leases and Capacity Purchase Agreements - Components of Lease Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Leases [Abstract]
Operating lease cost	$ 1,038	$ 1,213	$ 1,433
Variable and short-term lease cost	2,548	2,569	2,209
Amortization of finance lease assets	68	75	77
Interest on finance lease liabilities	85	44	24
Sublease income	(32)	(38)	(36)
Total lease cost	$ 3,707	$ 3,863	$ 3,707

Leases and Capacity Purchase _4

Leases and Capacity Purchase Agreements - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)Aircraftaircraft	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Lessee, Lease, Description [Line Items]
Additional leases that have not yet commenced | $		$ 500
United Airlines, Inc. | Bombardier CRJ-550
Lessee, Lease, Description [Line Items]
Number of aircraft operated under CPA		54
Term of CPA		10 years
United Airlines, Inc. | Embraer E175 LL
Lessee, Lease, Description [Line Items]
Number of aircraft operated under CPA		20
United Airlines, Inc. | Embraer E175
Lessee, Lease, Description [Line Items]
Number of aircraft operated under CPA		42
Term of CPA		5 years
United Airlines, Inc. | Cash Collateralized Letters of Credit
Lessee, Lease, Description [Line Items]
Number of regional aircraft | Aircraft		581
Mainline Aircraft
Lessee, Lease, Description [Line Items]
Number of aircraft subject to operating leases		114
Number of aircraft subject to finance leases		28
Regional Aircraft
Lessee, Lease, Description [Line Items]
Number of aircraft subject to operating leases		325
Number of aircraft subject to finance leases		17
Regional Aircraft | United Airlines, Inc. | Capacity Purchase Agreements
Lessee, Lease, Description [Line Items]
Expenses | $		$ 1,000	$ 979	$ 907
Accounts payable | $		$ 69	$ 53
Minimum | Mainline Aircraft
Lessee, Lease, Description [Line Items]
Initial term of operating leases		1 month
Minimum | Non-Aircraft
Lessee, Lease, Description [Line Items]
Initial term of operating leases		1 month
Maximum
Lessee, Lease, Description [Line Items]
Lease terms of additional leases that have not yet commenced (up to)		13 years
Maximum | Mainline Aircraft
Lessee, Lease, Description [Line Items]
Initial term of operating leases		10 years
Maximum | Non-Aircraft
Lessee, Lease, Description [Line Items]
Initial term of operating leases		34 years
Forecast | Capacity Purchase Agreements
Lessee, Lease, Description [Line Items]
Scheduled block hours increase (decrease) percentage	10.00%
Change in cash obligation | $	$ 202

Leases and Capacity Purchase _5

Leases and Capacity Purchase Agreements - Summary of Scheduled Future Minimum Lease Payments under Operating and Finance Leases (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	[1]
Operating Leases
2020	$ 920
2021	754
2022	591
2023	633
2024	626
After 2024	4,214
Minimum lease payments	7,738
Imputed interest	(2,106)
Present value of minimum lease payments	5,632
Less: current maturities of lease obligations	(686)	$ (719)
Long-term lease obligations	4,946	5,276
Finance Leases
2020	62
2021	75
2022	49
2023	38
2024	35
After 2024	57
Minimum lease payments	316
Imputed interest	(50)
Present value of minimum lease payments	266
Less: current maturities of lease obligations	(46)	(123)
Long-term lease obligations	$ 220	$ 224
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Leases and Capacity Purchase _6

Leases and Capacity Purchase Agreements - Additional Information Related to Leases (Details)	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Weighted-average remaining lease term - operating leases	11 years	10 years
Weighted-average remaining lease term - finance leases	6 years	5 years
Weighted-average discount rate - operating leases	5.20%	5.20%
Weighted-average discount rate - finance leases	5.70%	45.80%

Leases and Capacity Purchase _7

Leases and Capacity Purchase Agreements - Supplemental Cash Flow Information Related to Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases	$ 902	$ 1,078		$ 1,451
Operating cash flows for finance leases	70	53		24
Financing cash flows for finance leases	$ 151	$ 79	[1]	$ 84	[1]
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Leases and Capacity Purchase _8

Leases and Capacity Purchase Agreements - Future Lease Payment under Terms of Capacity Purchase Agreement (Details) $ in Billions	Dec. 31, 2019USD ($)
Leases [Abstract]
2020	$ 2.9
2021	2.9
2022	2.4
2023	1.5
2024	1.3
After 2024	4.7
Total	$ 15.7

Variable Interest Entities ("_2

Variable Interest Entities ("VIE") (Details) $ in Billions	Dec. 31, 2019USD ($)aircraft
Tax-Exempt Special Facilities Revenue Bonds
Variable Interest Entity [Line Items]
Underlying debt and interest | $	$ 1.9
Mainline Aircraft
Variable Interest Entity [Line Items]
Aircraft under operating lease, fixed purchase options	6
Regional Aircraft
Variable Interest Entity [Line Items]
Aircraft under operating lease	60

Commitments and Contingencies -

Commitments and Contingencies - Firm Commitments and Options to Purchase Aircraft (Details) - Dec. 31, 2019	commitment	aircraft
Airbus A321XLR
Long-term Purchase Commitment [Line Items]
Number of firm commitments | commitment	50
Scheduled aircraft deliveries in 2020		0
Scheduled aircraft deliveries after 2020		50
Airbus A350
Long-term Purchase Commitment [Line Items]
Number of firm commitments | commitment	45
Scheduled aircraft deliveries in 2020		0
Scheduled aircraft deliveries after 2020		45
Boeing 737 MAX
Long-term Purchase Commitment [Line Items]
Number of firm commitments | commitment	171
Scheduled aircraft deliveries in 2020		44
Scheduled aircraft deliveries after 2020		127
Boeing 777-300ER
Long-term Purchase Commitment [Line Items]
Number of firm commitments | commitment	2
Scheduled aircraft deliveries in 2020		2
Scheduled aircraft deliveries after 2020		0
Boeing 787
Long-term Purchase Commitment [Line Items]
Number of firm commitments | commitment	16
Scheduled aircraft deliveries in 2020		15
Scheduled aircraft deliveries after 2020		1
Embraer E175
Long-term Purchase Commitment [Line Items]
Number of firm commitments	20	20
Scheduled aircraft deliveries in 2020		20
Scheduled aircraft deliveries after 2020		0

Commitments and Contingencies_2

Commitments and Contingencies - Narrative (Details) $ / shares in Units, Employee in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)Option	Dec. 31, 2019$ / shares	Dec. 31, 2019shares	Dec. 31, 2019Employee	Dec. 31, 2019commitment	Dec. 31, 2019aircraft	Dec. 31, 2018USD ($)
Commitments and Contingencies [Line Items]
Aggregate balance	$ 15,700,000,000
Number of call options to purchase regional jet aircraft | Option	325
United Airlines, Inc.
Commitments and Contingencies [Line Items]
Number of employees | Employee				96
Percentage of employees represented by various U.S. labor organizations	84.00%
United Airlines, Inc. | Surety Bonds
Commitments and Contingencies [Line Items]
Long-term line of credit	$ 414,000,000
Tax-Exempt Special Facilities Revenue Bonds
Commitments and Contingencies [Line Items]
Guarantor obligations, maximum exposure	1,900,000,000
Tax-Exempt Special Facilities Revenue Bonds | Indirect Guarantee of Indebtedness
Commitments and Contingencies [Line Items]
Guarantor obligations, maximum exposure	175,000,000
Contingent liabilities based on participation	1,900,000,000
Floating Rate Debt
Commitments and Contingencies [Line Items]
Debt instrument principal amount	$ 3,400,000,000
Debt instrument, remaining terms	11 years
Loans And Leases From Non U S Entities
Commitments and Contingencies [Line Items]
Debt instrument, remaining terms	11 years
Aggregate balance	$ 3,200,000,000
Aircraft Mortgage Debt
Commitments and Contingencies [Line Items]
Guarantor obligations, maximum exposure	132,000,000
Kingsland
Commitments and Contingencies [Line Items]
Number of shares that may be put to United (in shares) | shares			144,800,000
Number of ADRs that may be put to United (in shares) | shares			18,100,000
Market price of common stock at fifth anniversary (in dollars per share) | $ / shares		$ 12
Aggregate maximum possible combined put payment and guarantee amount	217,000,000
Contingent liabilities based on participation							$ 31,000,000
Pass-Through Certificates
Commitments and Contingencies [Line Items]
Remaining proceeds from issuance of debt to be received in future periods	328,000,000
Debt instrument principal amount	2,234,000,000
Embraer E175
Commitments and Contingencies [Line Items]
Number of firm commitments					20	20
Number of aircraft scheduled for delivery | aircraft						20
Airbus A319
Commitments and Contingencies [Line Items]
Number of firm commitments | aircraft						20
Boeing 737-700
Commitments and Contingencies [Line Items]
Number of firm commitments | aircraft						19
Boeing 737 MAX
Commitments and Contingencies [Line Items]
Number of firm commitments | commitment					171
Number of aircraft scheduled for delivery | aircraft						44
Number of aircraft the company planned to take delivery of in 2019 | aircraft						16
Number of aircraft the company planned to take delivery of in 2020 | aircraft						28
Letter of Credit | United Airlines, Inc. | Cash Collateralized Letters of Credit
Commitments and Contingencies [Line Items]
Long-term line of credit	$ 73,000,000

Commitments and Contingencies_3

Commitments and Contingencies - Summary of Commitments Related to the Acquisition of Aircraft (Details) $ in Billions	Dec. 31, 2019USD ($)
Commitments and Contingencies Disclosure [Abstract]
2020	$ 6.9
2021	4.3
2022	2
2023	1
2024	1.2
After 2024	11.3
Total	$ 26.7

Special Charges and Unrealize_3

Special Charges and Unrealized (Gains) Losses on Investments - Components of Special Charges (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Operating:
Impairment of assets	$ 102	$ 0	$ 61	$ 8	$ 232	$ 11	$ 111	$ 23	$ 171	$ 377		$ 25
Severance and benefit costs	2	2	6	6	7	9	11	14	16	41		116
Termination of an engine maintenance service agreement					64	0	0	0	0	64		0
(Gains) losses on sale of assets and other special charges	26	25	4	4	(2)	(3)	7	3	59	5		35
Total operating special charges	130	27	71	18	301	17	129	40	246	487	[1]	176	[1]
Nonoperating unrealized (gains) losses on investments	(81)	(21)	(34)	(17)	(56)	(29)	135	(45)	(153)	5		0
Total special charges and unrealized (gains) losses on investments	49	6	37	1	245	(12)	264	(5)	93	492		176
Income tax benefit	(11)	(2)	(8)	0	(55)	3	(59)	1	(21)	(110)		(63)
Income tax adjustments					(5)	0	0	0	0	(5)		(189)
Total operating special charges, net of income taxes and income tax adjustments	$ 38	$ 4	$ 29	$ 1	$ 185	$ (9)	$ 205	$ (4)	$ 72	$ 377		$ (76)
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Special Charges and Unrealize_4

Special Charges and Unrealized (Gains) Losses on Investments - Narrative (Details)	1 Months Ended	3 Months Ended									12 Months Ended
	May 31, 2018USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Mar. 31, 2017USD ($)Employee	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Special Charges [Line Items]
Write-off of unexercised aircraft purchase											$ 18,000,000
Other miscellaneous impairments											20,000,000
Severance and benefit costs		$ 2,000,000	$ 2,000,000	$ 6,000,000	$ 6,000,000	$ 7,000,000	$ 9,000,000	$ 11,000,000	$ 14,000,000		16,000,000	$ 41,000,000	$ 116,000,000
Charge related to a contract termination											25,000,000
Charge for the settlement of certain legal matters											18,000,000
Gain (loss) on the sale and disposition of assets											(14,000,000)		(11,000,000)
Other charges											2,000,000		12,000,000
Gains due to the change in fair value of derivatives											13,000,000
Gain on change in market value of equity investments												28,000,000
Fair value adjustments related to aircraft purchased off lease, write-off of unexercised aircraft purchase options and other impairments												66,000,000
Termination of an engine maintenance service agreement						64,000,000	0	0	0		0	64,000,000	0
Losses due to the change in fair value of derivatives												33,000,000
Impairment of assets		102,000,000	$ 0	$ 61,000,000	$ 8,000,000	$ 232,000,000	$ 11,000,000	$ 111,000,000	$ 23,000,000		171,000,000	377,000,000	25,000,000
Weather-related damages													12,000,000
Aircraft Engines
Special Charges [Line Items]
Impairment of assets removed from operations											43,000,000
Obsolete Spare Parts Inventory
Special Charges [Line Items]
Impairment of assets													10,000,000
Maintenance Service Agreement
Special Charges [Line Items]
Intangible assets impairment charge													15,000,000
Management Reorganization Initiative
Special Charges [Line Items]
Severance and benefit costs													33,000,000
International Brotherhood of Teamsters
Special Charges [Line Items]
Severance and benefit costs											2,000,000	22,000,000	$ 83,000,000
International Brotherhood of Teamsters | Voluntary Early Out Program
Special Charges [Line Items]
Number of technicians and related employees electing to voluntarily separate from the Company | Employee										1,000
Severance payment per participant										$ 100,000
Management
Special Charges [Line Items]
Severance and benefit costs											14,000,000	19,000,000
Hong Kong Routes
Special Charges [Line Items]
Intangible assets impairment charge		$ 90,000,000										$ 206,000,000
Brazil Routes
Special Charges [Line Items]
Intangible assets impairment charge	$ 105,000,000
Azul
Special Charges [Line Items]
Gain on change in market value of equity investments											$ 140,000,000

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Unaudited) - Summary of Selected Quarterly FInancial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	[1]	Dec. 31, 2017	[1]
Quarterly Financial Information Disclosure [Abstract]
Operating revenue	$ 10,888	$ 11,380	$ 11,402	$ 9,589	$ 10,491	$ 11,003	$ 10,777	$ 9,032	$ 43,259	$ 41,303		$ 37,784
Income from operations	861	1,473	1,472	495	635	1,187	1,145	262	4,301	3,229		3,618
Net income	$ 641	$ 1,024	$ 1,052	$ 292	$ 461	$ 833	$ 683	$ 145	$ 3,009	$ 2,122	[2],[3],[4]	$ 2,143	[2],[3],[4]
Earnings per share, basic (in dollars per share)	$ 2.54	$ 4.01	$ 4.03	$ 1.09	$ 1.70	$ 3.06	$ 2.48	$ 0.51	$ 11.63	$ 7.70		$ 7.08
Earnings per share, diluted (in dollars per share)	$ 2.53	$ 3.99	$ 4.02	$ 1.09	$ 1.69	$ 3.05	$ 2.48	$ 0.51	$ 11.58	$ 7.67		$ 7.06
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[2]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8
[3]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[4]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Selected Quarterly Financial _4

Selected Quarterly Financial Data (Unaudited) - Impact of Significant Items on Quarterly Results (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Impairment of assets	$ 102	$ 0	$ 61	$ 8	$ 232	$ 11	$ 111	$ 23	$ 171	$ 377		$ 25
Severance and benefit costs	2	2	6	6	7	9	11	14	16	41		116
Termination of an engine maintenance service agreement					64	0	0	0	0	64		0
(Gains) losses on sale of assets and other special charges	26	25	4	4	(2)	(3)	7	3	59	5		35
Total operating special charges	130	27	71	18	301	17	129	40	246	487	[1]	176	[1]
Nonoperating unrealized (gains) losses on investments	(81)	(21)	(34)	(17)	(56)	(29)	135	(45)	(153)	5		0
Total special charges and unrealized (gains) losses on investments	49	6	37	1	245	(12)	264	(5)	93	492		176
Income tax benefit related to special charges and unrealized (gains) losses on investments	(11)	(2)	(8)	0	(55)	3	(59)	1	(21)	(110)		(63)
Income tax adjustments					(5)	0	0	0	0	(5)		(189)
Total operating special charges, net of income taxes and income tax adjustments	$ 38	$ 4	$ 29	$ 1	$ 185	$ (9)	$ 205	$ (4)	$ 72	$ 377		$ (76)
[1]	Amounts adjusted due to the adoption of Accounting Standards Update No. 2016-02, Leases (Topic 842) . See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

Subsequent Events (Details)

Subsequent Events (Details) - Subsequent Event	12 Months Ended
	Dec. 31, 2020	Feb. 24, 2020
China
Subsequent Event [Line Items]
Decline in near-term demand due to Level 4 travel advisory		100.00%
China | Forecast
Subsequent Event [Line Items]
Percent of planned capacity impacted by Level 4 travel advisory	5.00%
Other Trans-Pacific Countries
Subsequent Event [Line Items]
Decline in near-term demand due to Level 4 travel advisory		75.00%
Other Trans-Pacific Countries | Forecast
Subsequent Event [Line Items]
Percent of planned capacity impacted by Level 4 travel advisory	10.00%

Schedule II - Valuation and Q_2

Schedule II - Valuation and Qualifying Accounts (Details) - UAL and United - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for doubtful accounts
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 8	$ 7	$ 10
Additions Charged to Costs and Expenses	17	17	20
Deductions	16	16	23
Other	0	0	0
Balance at End of Period	9	8	7
Obsolescence allowance-spare parts
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	412	354	295
Additions Charged to Costs and Expenses	76	73	75
Deductions	63	15	17
Other	0	0	1
Balance at End of Period	425	412	354
Valuation allowance for deferred tax assets
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	59	63	68
Additions Charged to Costs and Expenses	0	2	11
Deductions	1	6	27
Other	0	0	11
Balance at End of Period	$ 58	$ 59	$ 63

Uncategorized Items - ual201910

Label	Element	Value
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 0
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(6,000,000)
AOCI Attributable to Parent [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 6,000,000