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FINANCIAL DERIVATIVE INSTRUMENTS - Location and Amount Recognized in Income by Hedging Relationship (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Cash Flow Hedging
Derivative [Line Items]
Amount of gain (loss) reclassified from AOCI into income	$ 99	$ 231
Cash Flow Hedging | Fuel derivative contracts
Derivative [Line Items]
Amount of gain (loss) reclassified from AOCI into income	99	238
Cash Flow Hedging | Other
Derivative [Line Items]
Amount of gain (loss) reclassified from AOCI into income	0	(7)
Fuel and oil
Derivative [Line Items]
Derivatives designated as hedging instruments	72	(128)
Fuel and oil | Cash Flow Hedging | Fuel derivative contracts
Derivative [Line Items]
Amount of gain (loss) reclassified from AOCI into income	72	(128)
Fuel and oil | Cash Flow Hedging | Other
Derivative [Line Items]
Amount of gain (loss) reclassified from AOCI into income	0	0
Other operating expenses
Derivative [Line Items]
Derivatives designated as hedging instruments	8	7
Other operating expenses | Cash Flow Hedging | Fuel derivative contracts
Derivative [Line Items]
Amount of gain (loss) reclassified from AOCI into income	0	0
Other operating expenses | Cash Flow Hedging | Other
Derivative [Line Items]
Amount of gain (loss) reclassified from AOCI into income	$ 8	$ 7

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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
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Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

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-Topic 815
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-Section 50
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Amount, before tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
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