v3.24.0.1
Long-term Debt, Short-term Borrowings and Finance Lease Obligations - Payroll Loans (Details)
$ / shares in Units, shares in Millions
1 Months Ended 12 Months Ended
May 06, 2021
USD ($)
$ / shares
shares
Jan. 15, 2021
USD ($)
$ / shares
shares
Apr. 23, 2020
USD ($)
$ / shares
shares
Feb. 12, 2024
USD ($)
Dec. 31, 2023
USD ($)
Dec. 31, 2022
USD ($)
Dec. 31, 2021
USD ($)
Dec. 31, 2020
USD ($)
Apr. 30, 2023
USD ($)
Sep. 29, 2020
Dec. 31, 2018
USD ($)
aircraft
Debt Instrument [Line Items]                      
CARES act, payroll support program, grant     $ 704,000,000                
Debt instrument term     10 years                
Class of warrant or right, outstanding (in shares) | shares     2.7                
Class of warrant or right, exercise price of warrants or rights (in dollars per share) | $ / shares     $ 9.50                
CARES act, payroll support program, total payment     $ 963,000,000                
Warrants and rights outstanding, term                   5 years  
Proceeds from sale leaseback transactions         $ 1,300,000,000 $ 0 $ 0 $ 563,000,000      
Proceeds from sale-leaseback transactions         $ 1,331,000,000 $ 0 $ 0 354,000,000      
Proceeds from sale-leaseback transactions               209,000,000      
Losses on sale-leaseback transactions               $ 106,000,000      
Subsequent Event                      
Debt Instrument [Line Items]                      
Proceeds from sale leaseback transactions       $ 174,000,000              
Payroll Support 2 Payments                      
Debt Instrument [Line Items]                      
CARES act, payroll support program, grant   $ 436,000,000                  
Debt instrument term   10 years                  
Class of warrant or right, outstanding (in shares) | shares   1.0                  
Class of warrant or right, exercise price of warrants or rights (in dollars per share) | $ / shares   $ 14.43                  
CARES Act, Payroll support program 2, total payment   $ 580,000,000                  
Payroll Support 3 Payments                      
Debt Instrument [Line Items]                      
CARES act, payroll support program, grant $ 409,000,000                    
Debt instrument term 10 years                    
Class of warrant or right, outstanding (in shares) | shares 0.7                    
Class of warrant or right, exercise price of warrants or rights (in dollars per share) | $ / shares $ 19.90                    
CARES act, payroll support program, total payment $ 541,000,000                    
Floating rate equipment notes, due through 2030                      
Debt Instrument [Line Items]                      
Debt instrument, face amount                 $ 78,000,000   $ 120,000,000
Floating rate equipment notes, due through 2030 | Secured Debt | A-320                      
Debt Instrument [Line Items]                      
Number of new aircraft held as security | aircraft                     6
Floating rate equipment notes, due through 2030 | Secured Debt | A-321                      
Debt Instrument [Line Items]                      
Number of new aircraft held as security | aircraft                     1
US Department of Treasury | Unsecured Debt                      
Debt Instrument [Line Items]                      
Debt instrument, face amount     $ 259,000,000                
Debt instrument, interest rate, stated percentage     1.00%                
US Department of Treasury | Unsecured Debt | Payroll Support 2 Payments                      
Debt Instrument [Line Items]                      
Debt instrument, face amount   $ 144,000,000                  
Debt instrument, interest rate, stated percentage   1.00%                  
US Department of Treasury | Unsecured Debt | Payroll Support 3 Payments                      
Debt Instrument [Line Items]                      
Debt instrument, face amount $ 132,000,000                    
Debt instrument, interest rate, stated percentage 1.00%                    
US Department of Treasury | Unsecured Debt | SOFR                      
Debt Instrument [Line Items]                      
Debt instrument, basis spread on variable rate     2.00%                
US Department of Treasury | Unsecured Debt | SOFR | Payroll Support 2 Payments                      
Debt Instrument [Line Items]                      
Debt instrument, basis spread on variable rate   2.00%                  
US Department of Treasury | Unsecured Debt | SOFR | Payroll Support 3 Payments                      
Debt Instrument [Line Items]                      
Debt instrument, basis spread on variable rate 2.00%