Debt and Other Obligations - Schedule of Interest Expense (Details) $ in Thousands	2 Months Ended	3 Months Ended		7 Months Ended	9 Months Ended
	Mar. 12, 2025 USD ($)	Sep. 30, 2025 USD ($) aircraft	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($) aircraft	Sep. 30, 2024 USD ($)	Mar. 18, 2025
Debt Instrument [Line Items]
Commitment and other fees	$ 20	$ 163	$ 412	$ 770	$ 1,247
Amortization of deferred financing costs and fair value adjustments	1,004	7,993	3,556	21,019	10,625
Total	47,682	$ 46,261	54,135	118,141	163,251
Accretion expense	0			0	3,157
Amortization of debt discount	0			$ 219	8,650
Aircraft
Debt Instrument [Line Items]
Failed aircraft sale leaseback | aircraft		18		18
Exit secured notes
Debt Instrument [Line Items]
Interest expense	0	$ 17,533	$ 0	$ 48,333	0
DIP term loan
Debt Instrument [Line Items]
Interest expense	$ 6,869			$ 0	$ 0
Secured Debt | 8.00% Senior Secured Notes
Debt Instrument [Line Items]
Stated interest rate percentage	8.00%	8.00%	8.00%	8.00%	8.00%
Interest expense	$ 17,753	$ 0	$ 23,252	$ 0	$ 69,757
Accretion expense			1,100		3,200
Interest expense			22,200		66,600
Amortization of debt discount		100		200
Secured Debt | Exit secured notes
Debt Instrument [Line Items]
Stated interest rate percentage						92.50%
Fixed-rate term loans
Debt Instrument [Line Items]
Interest expense	13,175	8,732	17,275	23,497	52,630
Amount of interest expense to be incurred if no bankruptcy		11,600		26,300
Unsecured term loans
Debt Instrument [Line Items]
Amount of interest expense to be incurred if no bankruptcy		800		2,400
Unsecured term loans | Payroll Support Program, CARES Act
Debt Instrument [Line Items]
Interest expense	265	579	343	2,178	1,028
Enhanced Equipment Trust Certificate | Class A 2015-1 EETC
Debt Instrument [Line Items]
Interest expense	1,879	2,305	2,531	5,088	7,649
Enhanced Equipment Trust Certificate | Class B 2015-1 EETC
Debt Instrument [Line Items]
Interest expense	0	0	0	0	446
Enhanced Equipment Trust Certificate | Class AA 2017-1 EETC
Debt Instrument [Line Items]
Interest expense	1,036	1,288	1,385	2,870	4,208
Enhanced Equipment Trust Certificate | Class A 2017-1 EETC
Debt Instrument [Line Items]
Interest expense	373	464	503	1,035	1,517
Enhanced Equipment Trust Certificate | Class B 2017-1 EETC
Debt Instrument [Line Items]
Interest expense	325	0	438	227	1,324
Enhanced Equipment Trust Certificate | Class B(R) 2025-1 EETC
Debt Instrument [Line Items]
Interest expense	0	6,964	0	12,876	0
Convertible notes
Debt Instrument [Line Items]
Convertible notes	1,246	0	4,432	0	12,795
Convertible notes | Convertible notes due 2026
Debt Instrument [Line Items]
Amortization of debt discount			4,400		13,300
Offset of favorable market-to-market adjustments					500
Exit secured notes
Debt Instrument [Line Items]
Amount of interest expense to be incurred if no bankruptcy				56,900
Exit secured notes | 2030 Senior Notes
Debt Instrument [Line Items]
Amount of interest expense to be incurred if no bankruptcy		26,100
Revolving credit facility
Debt Instrument [Line Items]
Interest expense	3,732	234	0	234	0
Revolving credit facility | Revolving credit facility due in 2026
Debt Instrument [Line Items]
Amount of interest expense to be incurred if no bankruptcy				1,900
Finance leases
Debt Instrument [Line Items]
Interest expense	$ 5	$ 6	$ 8	$ 14	$ 25