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
 3 Months Ended
Mar. 31, 2023
USD ($)
employee
Mar. 31, 2022
USD ($)
Dec. 31, 2022
USD ($)
Defined Benefit Plan Disclosure [Line Items]      
Curtailment gain   $ 33  
Curtailment gain, after tax   24  
Multiemployer plans, payment term 40 years    
National Master Agreement And Various Supplemental Agreements      
Defined Benefit Plan Disclosure [Line Items]      
Number of employees covered | employee 330,000    
Teamsters      
Defined Benefit Plan Disclosure [Line Items]      
Number of employees covered | employee 10,000    
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 $ 710   $ 686
Defined Benefit Pension Plan | Long term debt      
Defined Benefit Plan Disclosure [Line Items]      
Multiemployer plans, withdrawal obligation, present value 819   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 1,200    
Estimated future employer contributions to defined benefit plan, current fiscal year 78    
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 74    
Estimated future employer contributions to defined benefit plan, current fiscal year $ 44