FAIR VALUE MEASUREMENTS- Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Short-term investments	$ 1,127	$ 3,268
Fuel hedge contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
(Loss) gain recognized on derivatives	6	$ 394	$ 146
Fuel hedge contracts | Settlement Gains On Contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loss on derivative	58
Fuel hedge contracts | Mark-to-Market
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Gain on derivative	$ 52