REVENUE - Air Traffic Liability Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Air traffic liability
Beginning balance	$ 7,133	$ 5,510
Current period sales (passenger travel, ancillary services, flight loyalty, and partner loyalty)	14,702	9,348
Revenue from amounts included in contract liability opening balances	(2,945)	(2,317)
Revenue from current period sales	(11,165)	(5,408)
Ending balance	$ 7,725	$ 7,133