v3.26.3
Fair Value Measurements - Schedule of Carrying Amounts and Estimated Fair Values of the Company’s Debt (Details) - USD ($)
$ in Millions
Sep. 30, 2026
Dec. 31, 2025
Fair Value Disclosures [Abstract]    
Restricted cash $ 18 $ 17
Carrying
Value    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total debt 486 620
Estimated Fair Value    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total debt 472 626
Pre-delivery Credit Facilities | Carrying
Value | Secured Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total debt 180 348
Pre-delivery Credit Facilities | Estimated Fair Value | Secured Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total debt 182 352
2025-1 EETCs | Carrying
Value | Secured Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total debt 100 105
2025-1 EETCs | Estimated Fair Value | Secured Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total debt 100 109
Affinity card advance purchase of miles | Carrying
Value | Unsecured Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total debt 140 101
Affinity card advance purchase of miles | Estimated Fair Value | Unsecured Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total debt 125 100
PSP Promissory Notes | Carrying
Value | Unsecured Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total debt 66 66
PSP Promissory Notes | Estimated Fair Value | Unsecured Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total debt $ 65 $ 65