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, 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	881		881		881		881
Other comprehensive loss	(72)			(72)	(72)			(72)
Stock-settled share-based compensation	32	32			32	32
Other					(32)				(32)
Balance ending at Jun. 30, 2023	7,705	8,945	2,095	103	7,674	435	4,597	103	2,539
Balance beginning at Mar. 31, 2023	6,668	8,926	1,020	161	6,636	414	3,522	161	2,539
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,075		1,075		1,075		1,075
Other comprehensive loss	(58)			(58)	(58)			(58)
Stock-settled share-based compensation	21	21			21	21
Balance ending at Jun. 30, 2023	7,705	8,945	2,095	103	7,674	435	4,597	103	2,539
Balance beginning at Dec. 31, 2023	9,324	8,992	3,831	(62)	9,294	482	6,336	(62)	2,538
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,199		1,199		1,200		1,200
Other comprehensive loss	(35)			(35)	(35)			(35)
Stock-settled share-based compensation	56	56			56	56
Other					(20)				(20)
Balance ending at Jun. 30, 2024	10,526	9,001	4,986	(97)	10,495	538	7,536	(97)	2,518
Balance beginning at Mar. 31, 2024	9,188	8,973	3,664	(81)	9,158	507	6,212	(81)	2,520
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,323		1,323		1,324		1,324
Other comprehensive loss	(16)			(16)	(16)			(16)
Stock-settled share-based compensation	31	31			31	31
Other					(2)				(2)
Balance ending at Jun. 30, 2024	$ 10,526	$ 9,001	$ 4,986	$ (97)	$ 10,495	$ 538	$ 7,536	$ (97)	$ 2,518