Long-Term Debt, Finance Leases, and Other Borrowings - Schedule of Long-term Debt (Detail) - USD ($) $ in Thousands	Jun. 30, 2023	Sep. 30, 2022
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	$ 577,533	$ 615,310
Less unamortized debt issuance costs	(5,745)	(8,303)
Less notes payable warrants	(5,506)	(7,272)
Net long-term debt, including current maturities	566,282	599,735
Less current portion, net of unamortized debt issuance costs	(124,341)	(97,218)
Net long-term debt	441,941	502,517
Revolving credit facility quaterly collateralized by underlying equipment and investments through two thousand twenty eight [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	30,630	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]
Gross long-term debt, including current maturities	67,206	73,850
Notes Payable to Secured Parties, Due in Semi Annual Installments Collateralized by the Underlying Aircraft Through 2028 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	120,053	131,010
Notes Payable to Secured Parties, Due in Quarterly Installments Collateralized by the Underlying Aircraft Through 2028 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	94,571	106,865
United Bridge Loan Quaterly Collateralized By Underlying Equipment And Investments Through Two Thousand Twenty Four [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	2,622
Other Obligations Due to Financial Institutions, Monthly or Quarterly Collateralized by the Underlying Equipment, Due 2022 Through 2031 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	72,657	18,038
Notes Payable to Financial Institution, Due in Monthly Installments Collateralized by the Underlying Equipment, Through 2024 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	1,869	26,758
Notes Payable to Financial Institution, Due in Monthly Installments Secured by Flight Equipment, Through 2023 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities		2,000
Notes Payable to Financial Institution, Quarterly, Through 2027 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	144,400	204,947
Notes Payable to Financial Institution, Due in Monthly Installments Collateralized by the Underlying Equipment, Through 2027 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	$ 43,525	$ 36,212

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Amount of unamortized debt discount (premium) and debt issuance costs.

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Amount, excluding unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Sum of the carrying values as of the balance sheet date of the portions of all long-term notes and loans payable due within one year or the operating cycle if longer.

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