SEGMENTS - Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Segment Reporting Information, Profit (Loss)
Operating revenue	$ 13,748	$ 12,759
Depreciation and amortization	615	564
Operating (loss)/income	614	(277)
Interest expense, net	205	227
Total assets, end of period	74,969	73,134	$ 73,644
Capital expenditures	1,193	1,000
Operating Segments | Airline
Segment Reporting Information, Profit (Loss)
Operating revenue	12,563	11,843
Depreciation and amortization	615	564
Operating (loss)/income	565	(499)
Interest expense, net	205	227
Total assets, end of period	72,875	70,183
Capital expenditures	1,178	971
Operating Segments | Refinery
Segment Reporting Information, Profit (Loss)
Operating revenue	2,049	2,352
Depreciation and amortization	27	23
Operating (loss)/income	49	222
Interest expense, net	5	4
Total assets, end of period	2,123	3,005
Capital expenditures	15	29
Intersegment Sales/Other
Segment Reporting Information, Profit (Loss)
Operating revenue	(864)	(1,436)
Depreciation and amortization	(27)	(23)
Operating (loss)/income	0	0
Interest expense, net	(5)	(4)
Total assets, end of period	(29)	(54)
Capital expenditures	0	0
Intersegment Sales/Other | Sales to airline segment
Segment Reporting Information, Profit (Loss)
Operating revenue	(386)	(596)
Intersegment Sales/Other | Exchanged products
Segment Reporting Information, Profit (Loss)
Operating revenue	(439)	(714)
Intersegment Sales/Other | Sales of refined products
Segment Reporting Information, Profit (Loss)
Operating revenue	$ (39)	$ (126)