REVENUE - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) performanceObligation	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jul. 28, 2022 USD ($)	Dec. 31, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Modification of contract				$ 1,900
Residual travel funds (as a percent)	8.00%	9.00%			2.00%
Loyalty points, redemption period (in years)	1 year
Total operating revenues	$ 26,091	$ 23,814	$ 15,790
Revenue From Contract With Customer, Number Of Performance Obligations | performanceObligation	2
Other Revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total operating revenues	$ 2,100	$ 2,100	$ 1,400