Revenue Recognition - Passenger Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Operating revenue	$ 1,468	$ 12,536	$ 10,060	$ 23,008
Passenger
Disaggregation of Revenue [Line Items]
Operating revenue	678	11,368	8,247	20,622
Ticket
Disaggregation of Revenue [Line Items]
Operating revenue	568	9,969	7,078	17,957
Loyalty travel awards
Disaggregation of Revenue [Line Items]
Operating revenue	45	751	588	1,442
Travel-related services
Disaggregation of Revenue [Line Items]
Operating revenue	$ 65	$ 648	$ 581	$ 1,223