Financial Derivative Instruments - Location and Amount Recognized in Income by Hedging Relationship (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Cash Flow Hedging
Derivative [Line Items]
Amount of (gain) loss reclassified from AOCI into income	$ 147	$ 186	$ 804	$ 279
Cash Flow Hedging | Fuel derivative contracts
Derivative [Line Items]
Amount of (gain) loss reclassified from AOCI into income	140	192	792	275
Cash Flow Hedging | Interest rate derivative contracts
Derivative [Line Items]
Amount of (gain) loss reclassified from AOCI into income	7	(6)	12	4
Fuel and oil
Derivative [Line Items]
Derivatives designated as hedging instruments	(306)	12	(508)	28
Fuel and oil | Cash Flow Hedging | Fuel derivative contracts
Derivative [Line Items]
Amount of (gain) loss reclassified from AOCI into income	(306)	12	(508)	28
Fuel and oil | Cash Flow Hedging | Interest rate derivative contracts
Derivative [Line Items]
Amount of (gain) loss reclassified from AOCI into income	0	0	0	0
Other (gains)/losses, net
Derivative [Line Items]
Derivatives designated as hedging instruments			0	6
Other (gains)/losses, net | Cash Flow Hedging | Fuel derivative contracts
Derivative [Line Items]
Amount of (gain) loss reclassified from AOCI into income			0	6
Other (gains)/losses, net | Cash Flow Hedging | Interest rate derivative contracts
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	2	1	3	2
Other operating expenses | Cash Flow Hedging | Fuel derivative contracts
Derivative [Line Items]
Amount of (gain) loss reclassified from AOCI into income	0	0	0	0
Other operating expenses | Cash Flow Hedging | Interest rate derivative contracts
Derivative [Line Items]
Amount of (gain) loss reclassified from AOCI into income	$ 2	$ 1	$ 3	$ 2