COMMITMENTS AND CONTINGENCIES - Narrative (Details) $ in Millions	3 Months Ended
	Jun. 30, 2023 aircraft	Mar. 31, 2023 USD ($)	Sep. 30, 2023 USD ($)	Jan. 01, 2023
Commitments and Contingencies Disclosure [Abstract]
Future aircraft purchase commitments			$ 17,800
Future Purchase Commitments
Collective bargaining agreement term		4 years
Pilot pay rate increase				18.00%
Pilot agreement expense		$ 735
Adjustments to other benefit-related items		$ 130
A330-900
Future Purchase Commitments
Number of aircraft agreed to be acquired | aircraft	1
A220-300
Future Purchase Commitments
Number of aircraft purchase rights exercised | aircraft	12