REVENUE FROM CONTRACTS WITH CUSTOMERS - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Deferred Revenue Arrangement [Line Items]
Receivable	$ 510		$ 510		$ 383
Costs and Expenses	2,731	$ 2,628	7,704	$ 7,511
Mileage Plan Revenue [Member]
Deferred Revenue Arrangement [Line Items]
Contract liability revenue recognized			947	900
Receivable	105		105		$ 102
Mileage Plan Revenue [Member] | Mileage plan other revenue [Member]
Deferred Revenue Arrangement [Line Items]
Contract liability revenue recognized			(113)	(86)
Passenger Revenue [Member]
Deferred Revenue Arrangement [Line Items]
Contract liability revenue recognized	$ 46	$ 33	$ 763	$ 621