FAIR VALUE MEASUREMENTS (Tables)

12 Months Ended

Dec. 31, 2022

Fair Value Disclosures [Abstract]

Fair Value, by Balance Sheet Grouping [Table Text Block]

Fair values of financial instruments on the consolidated balance sheet (in millions):

	December 31, 2022						December 31, 2021
	Level 1		Level 2		Total		Level 1		Level 2		Total
Assets
Marketable securities
U.S. government and agency securities	$	505	$	—	$	505	$	331	$	—	$	331
Equity mutual funds	5		—		5		6		—		6
Foreign government bonds	—		25		25		—		38		38
Asset-backed securities	—		261		261		—		311		311
Mortgage-backed securities	—		196		196		—		232		232
Corporate notes and bonds	—		1,025		1,025		—		1,663		1,663
Municipal securities	—		62		62		—		65		65
Total Marketable securities	510		1,569		2,079		337		2,309		2,646
Derivative instruments
Fuel hedge contracts - call options	—		44		44		—		81		81
Interest rate swap agreements	—		15		15		—		—		—
Total Assets	$	510	$	1,628	$	2,138	$	337	$	2,390	$	2,727
Liabilities
Derivative instruments
Interest rate swap agreements	—		—		—		—		(9)		(9)
Total Liabilities	$	—	$	—	$	—	$	—	$	(9)	$	(9)

Fixed-rate debt on the consolidated balance sheet and the estimated fair value of long-term fixed-rate debt (in millions):

	December 31, 2022		December 31, 2021
Total fixed rate debt	$	1,660	$	1,821
Estimated fair value	$	1,473	$	1,919

Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis

Certain assets and liabilities are recognized or disclosed at fair value on a nonrecurring basis, including property, plant and equipment, operating lease assets, goodwill, and intangible assets. These assets are subject to fair valuation when there is evidence of impairment. Refer to Note 2 for discussion regarding impairment charges recorded in the year.

Schedule of Realized Gain (Loss) [Table Text Block]

Proceeds from sales of marketable securities were $2.3 billion, $3.6 billion, and $2.3 billion in 2022, 2021, and 2020.

Schedule of Debt Investment Maturities [Table Text Block]

Maturities for marketable securities (in millions):

December 31, 2022	Cost Basis		Fair Value
Due in one year or less	$	431	$	421
Due after one year through five years	1,717		1,624
Due after five years	30		28
Total	$	2,178	$	2,073