Revenue - Passenger Revenue Breakout (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Operating revenue	$ 5,706	$ 4,694
Passenger
Disaggregation of Revenue [Line Items]
Operating revenue	5,105	4,135
Passenger non-loyalty
Disaggregation of Revenue [Line Items]
Operating revenue	4,082	3,364
Passenger loyalty - air transportation
Disaggregation of Revenue [Line Items]
Operating revenue	825	624
Passenger ancillary sold separately
Disaggregation of Revenue [Line Items]
Operating revenue	$ 198	$ 147