Long-Term Debt, Finance Leases, and Other Borrowings - Schedule of Long-term Debt (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Sep. 30, 2023
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	$ 400,069	$ 538,274
Less unamortized debt issuance costs	(2,927)	(5,083)
Less notes payable warrants	(3,729)	(4,913)
Net long-term debt, including current maturities	393,413	528,278
Less current portion, net of unamortized debt issuance costs	(94,373)	(163,550)
Net long-term debt	299,040	364,728
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	38,020	40,630
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		39,018
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	97,287	108,815
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	81,950	90,401
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		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]
Gross long-term debt, including current maturities	60,657	67,637
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		1,075
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		41,098
Notes Payable to Financial Institution, Quarterly, Through 2027 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	$ 122,155	$ 139,100