REVENUE - Air Traffic Liability Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Air traffic liability
Beginning balance	$ 8,250	$ 7,725
Current period sales (passenger travel, ancillary services, flight loyalty, and partner loyalty)	23,766	22,012
Revenue from amounts included in contract liability opening balances	(5,031)	(4,976)
Revenue from current period sales	(18,706)	(16,511)
Ending balance	$ 8,279	$ 8,250