COMMITMENTS AND CONTINGENCIES (Details) $ in Millions				3 Months Ended	12 Months Ended	40 Months Ended
	Feb. 03, 2022 USD ($) aircraft	Sep. 28, 2021 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($) aircraft	Dec. 31, 2020 USD ($)
Other Commitments [Line Items]
Decrease in operating lease liability			$ 343
Payment Guarantee
Other Commitments [Line Items]
Principal amount of guarantee					$ 79
Net present value of future principal and interest payments					89	$ 433
Leaseholds and Leasehold Improvements
Other Commitments [Line Items]
Construction payments			$ 343
Los Angeles World Airports
Other Commitments [Line Items]
Payments for airport projects						$ 410
Decrease in operating lease liability				$ (365)
Los Angeles World Airports | Leaseholds and Leasehold Improvements
Other Commitments [Line Items]
Construction payments				$ 365
Love Field Airport Modernization Corporation | Series 2010 Bonds
Other Commitments [Line Items]
Debt redeemed		$ 310
Interest expense		$ 7
Aircraft
Other Commitments [Line Items]
Committed expenditures, year one					1,800
Committed expenditures, year two					1,600
Committed expenditures, year three					1,100
Committed expenditures, year four					837
Committed expenditures, year five					961
Committed expenditures, year six and beyond					$ 6,900
Capital Addition Purchase Commitments | Subsequent Event
Other Commitments [Line Items]
Committed expenditures, year one	$ 474
Committed expenditures, year two	$ 254
737 MAX 8
Other Commitments [Line Items]
Number of aircrafts leased | aircraft					9
Number of aircraft orders | aircraft					130
Options - 737MAX (in units) | aircraft					238
737 MAX 8 | Capital Addition Purchase Commitments | Subsequent Event
Other Commitments [Line Items]
Number of aircraft orders | aircraft	12
737 MAX 7
Other Commitments [Line Items]
Number of aircraft orders | aircraft					264
737 MAX 7 | Capital Addition Purchase Commitments | Subsequent Event
Other Commitments [Line Items]
Number of aircraft orders | aircraft	12