FAIR VALUE MEASUREMENTS (Tables)

12 Months Ended

Dec. 31, 2024

Fair Value Disclosures [Abstract]

Fair Value, by Balance Sheet Grouping

Fair values of financial instruments on the consolidated balance sheet:

	December 31, 2024
(in millions)	Level 1		Level 2		Level 3		Total
Assets
Marketable securities
U.S. government and agency securities	$	292	$	—	$	—	$	292
Equity mutual funds	7		—		—		7
Asset-backed securities	—		127		7		134
Mortgage-backed securities	—		112		—		112
Corporate notes and bonds	—		696		2		698
Municipal securities and other	—		31		—		31
Total Marketable securities	299		966		9		1,274
Derivative instruments
Interest rate swap agreements	—		9		—		9
Total Assets	$	299	$	975	$	9	$	1,283

	December 31, 2023
(in millions)	Level 1		Level 2		Level 3		Total
Assets
Marketable securities
U.S. government and agency securities	$	387	$	—	$	—	$	387
Equity mutual funds	5		—		—		5
Foreign government bonds	—		10		—		10
Asset-backed securities	—		192		—		192
Mortgage-backed securities	—		115		—		115
Corporate notes and bonds	—		763		—		763
Municipal securities and other	—		38		—		38
Total Marketable securities	392		1,118		—		1,510
Derivative instruments
Fuel hedge contracts - call options	—		11		—		11
Interest rate swap agreements	—		8		—		8
Total Assets	$	392	$	1,137	$	—	$	1,529

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

(in millions)	December 31, 2024		December 31, 2023
Fixed-rate debt	$	2,946	$	1,515
Estimated fair value	$	2,844	$	1,382

Schedule of Debt Investment Maturities

Maturities for marketable securities:

December 31, 2024 (in millions)	Cost Basis		Fair Value
Due in one year or less	$	461	$	460
Due after one year through five years	720		705
Due after five years through ten years	95		92
Due after ten years	10		9
No maturity date	5		8
Total	$	1,291	$	1,274