Revenue Recognition - Revenue by Geographic Region (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Operating revenue	$ 29,899	$ 17,095	$ 47,007
Domestic
Disaggregation of Revenue [Line Items]
Operating revenue	24,320	13,339	33,382
Atlantic
Disaggregation of Revenue [Line Items]
Operating revenue	2,537	1,649	7,308
Latin America
Disaggregation of Revenue [Line Items]
Operating revenue	2,284	1,321	3,326
Pacific
Disaggregation of Revenue [Line Items]
Operating revenue	758	786	2,991
Passenger
Disaggregation of Revenue [Line Items]
Operating revenue	22,519	12,883	42,277
Passenger | Domestic
Disaggregation of Revenue [Line Items]
Operating revenue	18,468	10,041	30,465
Passenger | Atlantic
Disaggregation of Revenue [Line Items]
Operating revenue	1,777	1,171	6,326
Passenger | Latin America
Disaggregation of Revenue [Line Items]
Operating revenue	1,873	1,113	2,985
Passenger | Pacific
Disaggregation of Revenue [Line Items]
Operating revenue	$ 401	$ 558	$ 2,501