Unusual or Infrequently Occurring Items (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Unusual or Infrequent Item, or Both [Line Items]
Special items - operating	$ 146	$ 186	$ 180	$ 250
Special items - net non-operating	0	(6)	0	(6)
Fleet transition - impairment [Member]
Unusual or Infrequent Item, or Both [Line Items]
Special items - operating	41	186	67	199
Labor agreements
Unusual or Infrequent Item, or Both [Line Items]
Special items - operating	30	0	30	51
Integration costs
Unusual or Infrequent Item, or Both [Line Items]
Special items - operating	30	0	38	0
Litigation
Unusual or Infrequent Item, or Both [Line Items]
Special items - operating	$ 45	$ 0	$ 45	$ 0