Revenue Recognition - Revenue by Geographic Region (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
Domestic
Disaggregation of Revenue [Line Items]
Operating revenue	1,264	8,809	7,531	16,325
Atlantic
Disaggregation of Revenue [Line Items]
Operating revenue	119	2,129	1,113	3,416
Latin America
Disaggregation of Revenue [Line Items]
Operating revenue	26	831	889	1,800
Pacific
Disaggregation of Revenue [Line Items]
Operating revenue	59	767	527	1,467
Passenger
Disaggregation of Revenue [Line Items]
Operating revenue	678	11,368	8,247	20,622
Passenger | Domestic
Disaggregation of Revenue [Line Items]
Operating revenue	564	8,093	6,165	14,834
Passenger | Atlantic
Disaggregation of Revenue [Line Items]
Operating revenue	64	1,873	882	2,947
Passenger | Latin America
Disaggregation of Revenue [Line Items]
Operating revenue	18	753	783	1,614
Passenger | Pacific
Disaggregation of Revenue [Line Items]
Operating revenue	$ 32	$ 649	$ 417	$ 1,227