Revenue Recognition - Disaggregated Operating Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 605	$ 271
Total passenger revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	588	262
Fare
Disaggregation of Revenue [Line Items]
Total operating revenues	229	100
Total non-fare passenger revenue
Disaggregation of Revenue [Line Items]
Total operating revenues	359	162
Service fees
Disaggregation of Revenue [Line Items]
Total operating revenues	162	62
Baggage
Disaggregation of Revenue [Line Items]
Total operating revenues	130	67
Seat selection
Disaggregation of Revenue [Line Items]
Total operating revenues	54	24
Other
Disaggregation of Revenue [Line Items]
Total operating revenues	13	9
Other revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 17	$ 9