Statements of Consolidated Stockholders' Equity - USD ($) $ in Millions		Total		United Airlines, Inc.		Common Stock		Additional Capital Invested		Additional Capital Invested United Airlines, Inc.		Treasury Stock		Retained Earnings		Retained Earnings United Airlines, Inc.		Accumulated Other Comprehensive Income (Loss)		Accumulated Other Comprehensive Income (Loss) United Airlines, Inc.		Receivable from Related Parties, Net United Airlines, Inc.
Balance (in shares) at Dec. 31, 2017	[1]					287,000,000
Balance at Dec. 31, 2017		$ 8,788	[1]	$ 8,751	[2]	$ 3	[1]	$ 6,098	[1]	$ 1,787	[2]	$ (769)	[1]	$ 4,603	[1]	$ 8,201	[2]	$ (1,147)	[1]	$ (1,147)	[2]	$ (90)	[2]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		145	[1],[3],[4]	145	[2],[5],[6]									145	[1]	145	[2]
Other comprehensive income		33	[4]	33	[6]
Other comprehensive income		26		26														26		26
Dividend to UAL				(569)						(569)
Stock settled share-based compensation		15		15				15		15
Repurchases of common stock (in shares)						(7,800,000)
Repurchases of common stock		(569)										(569)
Net treasury stock issued for share-based awards (in shares)						200,000
Net treasury stock issued for share-based awards		(17)						(36)				24		(5)
Other				(18)												(7)				7		(18)
Balance (in shares) at Mar. 31, 2018	[1]					279,400,000
Balance at Mar. 31, 2018		$ 8,388	[1]	$ 8,350	[2]	$ 3	[1]	6,077	[1]	1,233	[2]	(1,314)	[1]	4,736	[1]	8,339	[2]	(1,114)	[1]	(1,114)	[2]	(108)	[2]
Balance (in shares) at Dec. 31, 2018		269,914,769		1,000		269,900,000	[1]
Balance at Dec. 31, 2018		$ 10,042	[1],[7]	$ 10,004	[2],[8]	$ 3	[1]	6,120	[1]	598	[2]	(1,993)	[1]	6,715	[1]	10,319	[2]	(803)	[1]	(803)	[2]	(110)	[2]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		292		293										292		293
Other comprehensive income		10		10														10		10
Dividend to UAL				(528)						(528)
Stock settled share-based compensation		14		14				14		14
Repurchases of common stock (in shares)						(6,100,000)
Repurchases of common stock		(527)										(527)
Net treasury stock issued for share-based awards (in shares)						500,000
Net treasury stock issued for share-based awards		$ (29)						(54)				33		(8)
Other				$ (30)																		(30)
Balance (in shares) at Mar. 31, 2019		264,271,125		1,000		264,300,000
Balance at Mar. 31, 2019		$ 9,802		$ 9,763		$ 3		$ 6,080		$ 84		$ (2,487)		$ 6,999		$ 10,612		$ (793)		$ (793)		$ (140)

[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 I, Item 1 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 I, Item 1 of this report for additional information.The accompanying Combined Notes to Condensed Consolidated Financial Statements are an integral part of these statements.

[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 I, Item 1 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 I, Item 1 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 I, Item 1 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 I, Item 1 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 I, Item 1 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 I, Item 1 of this report for additional information.