Revenue Recognition - Revenue by Geographic Region (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Operating revenue	$ 3,062	$ 12,560	$ 13,122	$ 35,568
Domestic
Disaggregation of Revenue [Line Items]
Operating revenue	2,585	8,665	10,116	24,990
Atlantic
Disaggregation of Revenue [Line Items]
Operating revenue	240	2,338	1,353	5,754
Latin America
Disaggregation of Revenue [Line Items]
Operating revenue	126	747	1,015	2,547
Pacific
Disaggregation of Revenue [Line Items]
Operating revenue	111	810	638	2,277
Passenger
Disaggregation of Revenue [Line Items]
Operating revenue	1,938	11,410	10,185	32,032
Passenger | Domestic
Disaggregation of Revenue [Line Items]
Operating revenue	1,647	7,985	7,812	22,819
Passenger | Atlantic
Disaggregation of Revenue [Line Items]
Operating revenue	132	2,062	1,014	5,009
Passenger | Latin America
Disaggregation of Revenue [Line Items]
Operating revenue	97	673	879	2,287
Passenger | Pacific
Disaggregation of Revenue [Line Items]
Operating revenue	$ 62	$ 690	$ 480	$ 1,917