Long-Term Debt, Finance Leases, and Other Borrowings - Schedule of Long-term Debt (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Debt Instrument [Line Items]
Long-Term Debt, Gross	$ 538,274	$ 615,310
Less unamortized debt issuance costs	(5,083)	(8,303)
Less notes payable warrants	(4,913)	(7,272)
Net long-term debt, including current maturities	528,278	599,735
Less current portion, net of unamortized debt issuance costs	(163,550)	(97,218)
Net long-term debt	364,728	502,517
Revolving credit facility quaterly collateralized by underlying equipment and investments through two thousand twenty eight [Member]
Debt Instrument [Line Items]
Long-Term Debt, Gross	40,630	15,630
Senior and Subordinated Notes Payable to Secured Parties, Due in Monthly Installments Collateralized by the Underlying Aircraft Through 2027 [Member]
Debt Instrument [Line Items]
Long-Term Debt, Gross	39,018	73,850
Notes Payable to Secured Parties, Due in Semi Annual Installments Collateralized by the Underlying Aircraft Through 2028 [Member]
Debt Instrument [Line Items]
Long-Term Debt, Gross	108,815	131,010
Notes Payable to Secured Parties, Due in Quarterly Installments Collateralized by the Underlying Aircraft Through 2028 [Member]
Debt Instrument [Line Items]
Long-Term Debt, Gross	90,401	106,865
United Bridge Loan Quaterly Collateralized By Underlying Equipment And Investments Through Two Thousand Twenty Four [Member]
Debt Instrument [Line Items]
Long-Term Debt, Gross	10,500
Other Obligations Due to Financial Institutions, Monthly or Quarterly Collateralized by the Underlying Equipment, Due 2022 Through 2031 [Member]
Debt Instrument [Line Items]
Long-Term Debt, Gross	67,637	18,038
Notes Payable to Financial Institution, Due in Monthly Installments Collateralized by the Underlying Equipment, Through 2024 [Member]
Debt Instrument [Line Items]
Long-Term Debt, Gross	1,075	26,758
Notes Payable to Financial Institution, Due in Monthly Installments Secured by Flight Equipment, Through 2023 [Member]
Debt Instrument [Line Items]
Long-Term Debt, Gross		2,000
Notes Payable to Financial Institution, Due in Monthly Installments Collateralized by the Underlying Equipment, Through 2027 [Member]
Debt Instrument [Line Items]
Long-Term Debt, Gross	41,098	36,212
Notes Payable To Financial Institution Due Two Thousand Twenty Three [Member]
Debt Instrument [Line Items]
Long-Term Debt, Gross	$ 139,100	$ 204,947