REVENUE RECOGNITION - Revenue by Geographic Region (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Operating revenue	$ 15,578	$ 13,824	$ 28,337	$ 23,173
Domestic
Disaggregation of Revenue [Line Items]
Operating revenue	10,749	10,655	20,145	18,204
Atlantic
Disaggregation of Revenue [Line Items]
Operating revenue	3,178	2,057	4,726	2,833
Latin America
Disaggregation of Revenue [Line Items]
Operating revenue	1,037	854	2,317	1,665
Pacific
Disaggregation of Revenue [Line Items]
Operating revenue	614	258	1,149	471
Passenger
Disaggregation of Revenue [Line Items]
Operating revenue	13,205	10,958	23,616	17,865
Passenger | Domestic
Disaggregation of Revenue [Line Items]
Operating revenue	8,944	8,318	16,538	13,881
Passenger | Atlantic
Disaggregation of Revenue [Line Items]
Operating revenue	2,803	1,701	4,047	2,240
Passenger | Latin America
Disaggregation of Revenue [Line Items]
Operating revenue	926	745	2,058	1,425
Passenger | Pacific
Disaggregation of Revenue [Line Items]
Operating revenue	$ 532	$ 194	$ 973	$ 319