Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2025

Fair Value Disclosures [Abstract]

Schedule of Carrying Amount and Estimated Fair Value, Long-term Debt

The carrying amounts and estimated fair values of the Company's long-term debt at March 31, 2025 and December 31, 2024 were as follows (in millions):

	March 31, 2025				December 31, 2024				Fair Value Level Hierarchy
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
DIP term loans	$	—	$	—	$	309.0	$	309.0	Level 3
Fixed-rate term loans	904.9		903.3		972.2		970.7		Level 3
Unsecured term loans	136.3		130.0		136.3		130.4		Level 3
2015-1 EETC Class A	234.6		216.2		234.6		215.8		Level 2
2017-1 EETC Class AA	154.3		136.7		160.3		140.4		Level 2
2017-1 EETC Class A	51.4		44.5		53.4		45.8		Level 2
2017-1 EETC Class B	43.0		42.8		44.7		40.5		Level 2
Revolving credit facility	—		—		300.0		300.0		Level 3
2025-1 EETC Class B	215.0		212.9		—		—		Level 2
Exit Secured Notes	841.8		802.4		—		—		Level 3
Total long-term debt	$	2,581.3	$	2,488.8	$	2,210.5	$	2,152.6
8.00% senior secured notes	$	—	$	—	$	1,110.0	$	1,117.9	Level 3
4.75% convertible notes due 2025	—		—		25.1		8.8		Level 2
1.00% convertible notes due 2026	—		—		500.0		166.4		Level 2
Total liabilities subject to compromise	$	—	$	—	$	1,635.1	$	1,293.1

Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis

Assets and liabilities measured at gross fair value on a recurring basis are summarized below (in millions):

	Successor Fair Value Measurements as of March 31, 2025
	Total		Level 1		Level 2		Level 3
Cash and cash equivalents	$	487.5	$	487.5	$	—	$	—
Restricted cash	270.5		270.5		—		—
Short-term investment securities	119.6		119.6		—		$	—
Assets held for sale	447.6		—		—		$	447.6
Total assets	$	1,325.2	$	877.6	$	—	$	447.6
Total liabilities	$	—	$	—	$	—	$	—

	Predecessor Fair Value Measurements as of December 31, 2024
	Total		Level 1		Level 2		Level 3
Cash and cash equivalents	$	902.1	$	902.1	$	—	$	—
Restricted cash	168.4		168.4		—		—
Short-term investment securities	118.3		118.3		—		—
Assets held for sale	463.0		—		—		463.0
Total assets	$	1,651.8	$	1,188.8	$	—	$	463.0
Total liabilities	$	—	$	—	$	—	$	—