Revenue - Air Traffic Liability Breakout (Details) - USD ($) $ in Millions	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Air traffic liability - passenger travel and ancillary passenger services	$ 4,004		$ 3,061
Air traffic liability - loyalty program	4,996	$ 5,079	5,189	$ 4,885	$ 4,885	$ 4,789
Total Air traffic liability	$ 9,000		$ 8,250	$ 8,425		$ 7,725