DERIVATIVE INSTRUMENTS - BALANCE SHEET CLASSIFICATION (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Accumulated other comprehensive loss	$ (299)	$ (388)	$ (262)	$ (494)
Fuel hedge contracts [Member] | Derivative Instruments Not Designated as Hedges [Member] | Fuel Hedge Contracts, Current [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets, Current	10	33
Fuel hedge contracts [Member] | Derivative Instruments Not Designated as Hedges [Member] | Fuel Hedge Contracts, Noncurrent [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets, Current	1	11
Interest rate swaps agreements [Member] | Derivative Instruments Designated as Hedges [Member] | Prepaid Expenses and Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets, Current	6	8
Interest rate swaps agreements [Member] | Derivative Instruments Designated as Hedges [Member] | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets, Current	2	7
Interest rate swaps agreements [Member] | Derivative Instruments Designated as Hedges [Member] | Accumulated Other Comprehensive Loss [Member]
Derivatives, Fair Value [Line Items]
Accumulated other comprehensive loss	$ (7)	$ 23