Quarterly report pursuant to Section 13 or 15(d)

EMPLOYEE BENEFIT PLANS - Additional Information (Details)

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EMPLOYEE BENEFIT PLANS - Additional Information (Details)
$ in Millions
 1 Months Ended 9 Months Ended
Jan. 31, 2023
USD ($)
Sep. 30, 2023
USD ($)
employee
Sep. 30, 2022
USD ($)
Sep. 09, 2023
USD ($)
Dec. 31, 2022
USD ($)
Defined Benefit Plan Disclosure [Line Items]          
Curtailment gain     $ 33    
Curtailment gain, after tax     24    
Multiemployer plans, payment term   39 years      
Central States Pension Fund          
Defined Benefit Plan Disclosure [Line Items]          
Government assistance, amount $ 35,800        
National Master Agreement and Various Supplemental Agreements          
Defined Benefit Plan Disclosure [Line Items]          
Number of employees covered | employee   300,000      
Teamsters          
Defined Benefit Plan Disclosure [Line Items]          
Number of employees covered | employee   10,000      
Projected benefit obligation, expected increase for modification       $ 600  
Independent Pilots Association          
Defined Benefit Plan Disclosure [Line Items]          
Number of employees covered | employee   3,500      
Teamsters Local 2727          
Defined Benefit Plan Disclosure [Line Items]          
Number of employees covered | employee   1,800      
International Association Of Machinists And Aerospace Workers          
Defined Benefit Plan Disclosure [Line Items]          
Number of employees covered | employee   3,100      
Defined Benefit Pension Plan          
Defined Benefit Plan Disclosure [Line Items]          
Multi-employer plans, withdrawal obligation, fair value   $ 642     $ 686
Defined Benefit Pension Plan | Long term debt          
Defined Benefit Plan Disclosure [Line Items]          
Multiemployer plans, withdrawal obligation, present value   815     821
Defined Benefit Pension Plan | Other current liabilities          
Defined Benefit Plan Disclosure [Line Items]          
Multiemployer plans, withdrawal obligation, present value   8     $ 8
Defined Benefit Pension Plan | U.S. Pension Benefits          
Defined Benefit Plan Disclosure [Line Items]          
Curtailment gain   0 0    
Amount contributed to company- sponsored benefit plans   1,300      
Estimated future employer contributions to defined benefit plan, current fiscal year   26      
U.S. Postretirement Medical Benefits | U.S. Pension Benefits          
Defined Benefit Plan Disclosure [Line Items]          
Curtailment gain   0 $ 0    
Amount contributed to company- sponsored benefit plans   108      
Estimated future employer contributions to defined benefit plan, current fiscal year   $ 10