STATEMENTS OF CONSOLIDATED STOCKHOLDER'S EQUITY (UNAUDITED) (UA) - USD ($) $ in Millions	Total	Additional Capital Invested	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	United Airlines, Inc.	United Airlines, Inc. Additional Capital Invested	United Airlines, Inc. Retained Earnings	United Airlines, Inc. Accumulated Other Comprehensive Income (Loss)	United Airlines, Inc. Payable to Parent
Balance beginning at Dec. 31, 2021	$ 5,029	$ 9,156	$ 625	$ (942)	$ 4,998	$ 317	$ 2,977	$ (942)	$ 2,646
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(106)		(106)		(105)		(105)
Other comprehensive loss	(22)			(22)	(22)			(22)
Stock-settled share-based compensation	70	70			70	70
Other					(75)				(75)
Balance ending at Sep. 30, 2022	4,898	8,970	421	(964)	4,866	387	2,872	(964)	2,571
Balance beginning at Jun. 30, 2022	3,964	8,970	(515)	(944)	3,933	373	1,930	(944)	2,574
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	942		942		942		942
Other comprehensive loss	(20)			(20)	(20)			(20)
Stock-settled share-based compensation	15	15			14	14
Other					(3)				(3)
Balance ending at Sep. 30, 2022	4,898	8,970	421	(964)	4,866	387	2,872	(964)	2,571
Balance beginning at Dec. 31, 2022	6,896	8,986	1,265	175	6,865	403	3,716	175	2,571
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	2,018		2,018		2,019		2,019
Other comprehensive loss	(84)			(84)	(84)			(84)
Stock-settled share-based compensation	55	55			55	55
Other					(32)				(32)
Balance ending at Sep. 30, 2023	8,853	8,968	3,232	91	8,823	458	5,735	91	2,539
Balance beginning at Jun. 30, 2023	7,705	8,945	2,095	103	7,674	435	4,597	103	2,539
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	1,137		1,137		1,138		1,138
Other comprehensive loss	(12)			(12)	(12)			(12)
Stock-settled share-based compensation	23	23			23	23
Balance ending at Sep. 30, 2023	$ 8,853	$ 8,968	$ 3,232	$ 91	$ 8,823	$ 458	$ 5,735	$ 91	$ 2,539