Fair Value Measurements - Carrying Amounts and Estimated Fair Values of the Company’s Debt (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, fair value	$ 355	$ 423
Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, fair value	341	422
Pre-delivery credit facility | Carrying Value | Secured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, fair value	200	174
Pre-delivery credit facility | Estimated Fair Value | Secured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, fair value	201	175
Treasury Loan | Carrying Value | Secured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, fair value	0	150
Treasury Loan | Estimated Fair Value | Secured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, fair value	0	156
Floating rate building note | Carrying Value | Secured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, fair value	18	18
Floating rate building note | Estimated Fair Value | Secured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, fair value	18	19
PSP Promissory Notes | Carrying Value | Unsecured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, fair value	66	66
PSP Promissory Notes | Estimated Fair Value | Unsecured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, fair value	55	58
Affinity card advance purchase of mileage credits | Carrying Value | Unsecured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, fair value	71	15
Affinity card advance purchase of mileage credits | Estimated Fair Value | Unsecured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, fair value	$ 67	$ 14