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 loss	(194)		(194)		(194)		(194)
Other comprehensive loss	(14)			(14)	(14)			(14)
Stock-settled share-based compensation	11	11			11	11
Other					(32)				(32)
Balance ending at Mar. 31, 2023	6,668	8,926	1,020	161	6,636	414	3,522	161	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 loss	(124)		(124)		(124)		(124)
Other comprehensive loss	(19)			(19)	(19)			(19)
Stock-settled share-based compensation	25	25			25	25
Other					(18)				(18)
Balance ending at Mar. 31, 2024	$ 9,188	$ 8,973	$ 3,664	$ (81)	$ 9,158	$ 507	$ 6,212	$ (81)	$ 2,520