FINANCIAL DERIVATIVE INSTRUMENTS - Offsetting of Derivative Assets (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Fuel derivative contracts | Prepaid expenses and other current assets
Offsetting Assets
Gross amounts of recognized assets	$ 86	$ 352
Gross amounts of recognized liabilities	(15)	(106)
Net amounts of assets presented in the Balance Sheet	$ 71	$ 246
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Prepaid expenses and other current assets	Prepaid expenses and other current assets
Fuel derivative contracts | Other assets
Offsetting Assets
Gross amounts of recognized assets	$ 137	$ 160
Gross amounts of recognized liabilities	(35)	0
Net amounts of assets presented in the Balance Sheet	$ 102	$ 160
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Interest rate derivatives
Offsetting Assets
Net amounts of assets presented in the Balance Sheet	$ 0	$ 14
Interest rate derivatives | Other assets
Offsetting Assets
Gross amounts of recognized assets	0	14
Gross amounts of recognized liabilities	$ 0	$ 0
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets