REVENUE - Air Traffic Liability - Loyalty Program Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Air traffic liability
Beginning balance	$ 4,447	$ 3,385
Amounts deferred associated with points awarded	2,523	1,958
Unused funds converted to loyalty points	0	167
Ending balance	4,789	4,447
Passenger Customer
Air traffic liability
Revenue recognized from points redeemed	(2,136)	(1,003)
Other
Air traffic liability
Revenue recognized from points redeemed	$ (45)	$ (60)