Revenue - Passenger Revenue Breakout (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Operating revenue	$ 7,037	$ 6,728	$ 12,743	$ 11,422
Passenger
Disaggregation of Revenue [Line Items]
Operating revenue	6,409	6,119	11,514	10,254
Passenger non-loyalty
Disaggregation of Revenue [Line Items]
Operating revenue	5,183	5,118	9,265	8,482
Passenger loyalty - air transportation
Disaggregation of Revenue [Line Items]
Operating revenue	989	821	1,814	1,445
Passenger ancillary sold separately
Disaggregation of Revenue [Line Items]
Operating revenue	$ 237	$ 180	$ 435	$ 327