REVENUE - Passenger Revenue Breakout (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue
Total operating revenues	$ 23,814	$ 15,790	$ 9,048
Passenger
Disaggregation of Revenue
Total operating revenues	21,408	14,066	7,665
Passenger non-loyalty
Disaggregation of Revenue
Total operating revenues	17,645	11,377	6,303
Passenger loyalty - air transportation
Disaggregation of Revenue
Total operating revenues	3,028	2,136	1,003
Passenger ancillary sold separately
Disaggregation of Revenue
Total operating revenues	$ 735	$ 553	$ 359