Revenue - Passenger Revenue Breakout (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Disaggregation of Revenue [Line Items]
Total passenger revenues	$ 6,870	$ 6,525	$ 20,553	$ 19,268
Passenger
Disaggregation of Revenue [Line Items]
Total passenger revenues	6,250	5,912	18,673	17,426
Passenger non-loyalty
Disaggregation of Revenue [Line Items]
Total passenger revenues	5,092	4,758	15,316	14,023
Passenger loyalty - air transportation
Disaggregation of Revenue [Line Items]
Total passenger revenues	896	916	2,589	2,730
Passenger ancillary sold separately
Disaggregation of Revenue [Line Items]
Total passenger revenues	$ 262	$ 238	$ 768	$ 673