Financial Derivative Instruments - Location and Amount Recognized in Income by Hedging Relationship (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Cash Flow Hedging
Derivative [Line Items]
Amount of (gain) reclassified from AOCI into income	$ 127	$ (658)
Cash Flow Hedging | Fuel derivative contracts
Derivative [Line Items]
Amount of (gain) reclassified from AOCI into income	125	(654)
Cash Flow Hedging | Interest rate derivative contracts
Derivative [Line Items]
Amount of (gain) reclassified from AOCI into income	2	(4)
Fuel and oil
Derivative [Line Items]
Derivatives designated as hedging instruments	(28)	(203)
Fuel and oil | Cash Flow Hedging | Fuel derivative contracts
Derivative [Line Items]
Amount of (gain) reclassified from AOCI into income	(28)	(203)
Fuel and oil | Cash Flow Hedging | Interest rate derivative contracts
Derivative [Line Items]
Amount of (gain) reclassified from AOCI into income	0	0
Other operating expenses
Derivative [Line Items]
Derivatives designated as hedging instruments	2	2
Other operating expenses | Cash Flow Hedging | Fuel derivative contracts
Derivative [Line Items]
Amount of (gain) reclassified from AOCI into income	0	0
Other operating expenses | Cash Flow Hedging | Interest rate derivative contracts
Derivative [Line Items]
Amount of (gain) reclassified from AOCI into income	$ 2	$ 2