Statements of Consolidated Stockholder's Equity - USD ($) $ in Millions	Total		United Airlines, Inc.		Common Stock	Additional Capital Invested	Additional Capital Invested United 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, Net United Airlines, Inc.
Balance (in shares) at Dec. 31, 2015					364,600,000
Balance at Dec. 31, 2015	$ 8,966		$ 8,963		$ 4	$ 7,946	$ 6,138	$ (1,610)	$ 3,457		$ 3,673		$ (831)	$ (831)	$ (17)
Net income	2,234	[1],[2],[3],[4]	2,234	[5],[6],[7]					2,234	[4]	2,234	[7],[8]
Other comprehensive income (loss)	2		2	[5]									2	2
Stock-settled share-based compensation	32		32			32	32
Dividend to UAL			(2,603)				(2,603)
Proceeds from exercise of stock options / net treasury stock issued for share-based awards (in shares)					300,000
Proceeds from exercise of stock options	6					6
Repurchases of common stock (in shares)					(50,300,000)
Repurchases of common stock	(2,607)							(2,607)
Treasury stock retired					$ (1)	(1,415)		3,709	(2,293)
UAL contribution related to stock plans			6				6
Other	(59)		(114)					(3)	(56)		(56)				(58)
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	2,144	[1],[2],[3],[4]	2,163	[5],[6],[7]					2,144	[4]	2,163	[7],[8]
Other comprehensive income (loss)	(200)		(200)	[5]									(200)	(200)
Stock-settled share-based compensation	56		56			56	56
Dividend to UAL			(1,844)				(1,844)
Proceeds from exercise of stock options / net treasury stock issued for share-based awards (in shares)					200,000
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						(508)		1,576	(1,068)
Net treasury stock issued for share-based awards	$ (12)					(21)		10	(1)
UAL contribution related to stock plans			2				2
Reclassification of stranded tax effects									118		118		(118)	(118)
Other			$ (15)												(15)
Balance (in shares) at Dec. 31, 2017	286,973,195	[9]	1,000	[10]	287,000,000
Balance at Dec. 31, 2017	$ 8,734	[9]	$ 8,696	[10]	$ 3	6,098	1,787	(769)	4,549		8,146		(1,147)	(1,147)	(90)
Net income	2,129		2,131						2,129		2,131
Other comprehensive income (loss)	338		338										338	338
Stock-settled share-based compensation	$ 60		60			60	60
Dividend to UAL			(1,249)				(1,249)
Proceeds from exercise of stock options / net treasury stock issued for share-based awards (in shares)					400,000
Repurchases of common stock (in shares)	(17,500,000)				(17,500,000)
Repurchases of common stock	$ (1,250)							(1,250)
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		1,000		269,900,000
Balance at Dec. 31, 2018	$ 9,995		$ 9,957		$ 3	$ 6,120	$ 598	$ (1,993)	$ 6,668		$ 10,272		$ (803)	$ (803)	$ (110)

[1] Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) and Accounting Standards Update No. 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. 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. 2014-09, Revenue from Contracts with Customers (Topic 606). 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. 2014-09, Revenue from Contracts with Customers (Topic 606). 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. 2014-09, Revenue from Contracts with Customers (Topic 606). 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. 2014-09, Revenue from Contracts with Customers (Topic 606). 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. 2014-09, Revenue from Contracts with Customers (Topic 606). 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. 2014-09, Revenue from Contracts with Customers (Topic 606). 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. 2014-09, Revenue from Contracts with Customers (Topic 606) and Accounting Standards Update No. 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. 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. 2014-09, Revenue from Contracts with Customers (Topic 606). 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. 2014-09, Revenue from Contracts with Customers (Topic 606). See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.