LONG-TERM DEBT - LINE OF CREDIT (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Line of Credit Facility [Line Items]
Proceeds from Issuance of Secured Debt	$ 149	$ 0
Line of Credit Facility, Maximum Borrowing Capacity	626
Line of Credit Facility, Asset Restrictions	500
Credit Facility 1 [Member] | Secured by certain accounts receivable, spare engines, spare parts and ground service equipment [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	150
Credit Facility 2 [Member] | Secured by aircraft [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	400
Credit Facility 3 [Member] | Secured by aircraft [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	76
US Treasury CARES Act Loan [Member]
Line of Credit Facility [Line Items]
Adjustments to Additional Paid in Capital, Warrant Issued	$ 30