| Document and Entity Information - USD ($) $ in Thousands | 12 Months Ended | | |
| Sep. 30, 2023 | Sep. 30, 2022 | Dec. 27, 2023 | Mar. 31, 2023 |
| Cover [Abstract] | | | | |
| Document Type | 10-K/A | | | |
| Amendment Flag | true | | | |
| Amendment Description | Mesa Air Group, Inc.(“Mesa,” the “Company,” “we,” “us,” or “our”) is filing this Amendment No. 1 on Form 10-K/A (this “Amendment”) to amend our Annual Report on Form 10-K for the fiscal year ended September 30, 2023, originally filed with the Securities and Exchange Commission (the “SEC”) on January 26, 2024 (the “Original Filing”), as follows:•Items 10, 11, 12, 13 and 14. To includes Items 10, 11, 12, 13 and 14 of Part III of Form 10-K. We previously omitted this information from our Original Filing in reliance on General Instruction G(3) to Form 10-K, which permits the above-referenced items to be incorporated in our Form 10-K by reference to our definitive proxy statement if such statement is filed no later than 120 days after our fiscal year-end. We are filing this Amendment to provide the information required in Part III of Form 10-K because we will not file a definitive proxy statement containing that information within 120 days after the end of the fiscal year covered by our Original Filing. This Amendment amends and restates in their entirety Items 10, 11, 12, 13 and 14 of Part III of our Original Filing. The cover page of our Original Filing is also amended to delete the reference to the incorporation by reference to our definitive proxy statement. | | | |
| Document Period End Date | Sep. 30, 2023 | | | |
| Document Fiscal Year Focus | 2023 | | | |
| Document Fiscal Period Focus | FY | | | |
| Trading Symbol | MESA | | | |
| Entity Registrant Name | MESA AIR GROUP, INC. | | | |
| Entity Central Index Key | 0000810332 | | | |
| Current Fiscal Year End Date | --09-30 | | | |
| Entity Filer Category | Accelerated Filer | | | |
| Entity Well-known Seasoned Issuer | No | | | |
| Entity Current Reporting Status | Yes | | | |
| Entity Voluntary Filers | No | | | |
| Entity Interactive Data Current | Yes | | | |
| Entity Shell Company | false | | | |
| Entity Small Business | false | | | |
| Entity Emerging Growth Company | false | | | |
| ICFR Auditor Attestation Flag | true | | | |
| Entity Public Float | | | | $ 96,267,679 |
| Entity Common Stock, Shares Outstanding | | | 40,940,326 | |
| Entity File Number | 001-38626 | | | |
| Entity Incorporation, State or Country Code | NV | | | |
| Entity Tax Identification Number | 85-0302351 | | | |
| Entity Address, Address Line One | 410 NORTH 44TH STREET | | | |
| Entity Address, Address Line Two | SUITE 700 | | | |
| Entity Address, City or Town | PHOENIX | | | |
| Entity Address, State or Province | AZ | | | |
| Entity Address, Postal Zip Code | 85008 | | | |
| City Area Code | 602 | | | |
| Local Phone Number | 685-4000 | | | |
| Document Annual Report | true | | | |
| Document Transition Report | false | | | |
| Title of 12(b) Security | Common Stock, no par value | | | |
| Document Financial Statement Error Correction [Flag] | true | | | |
| Document Financial Statement Restatement Recovery Analysis [Flag] | false | | | |
| Security Exchange Name | NASDAQ | | | |
| Auditor Name | RSM US LLP | Ernst & Young LLP | | |
| Auditor Firm ID | 49 | 42 | | |
| Auditor Location | Phoenix Arizona | Phoenix, Arizona | | |
| Documents Incorporated by Reference | DOCUMENTS INCORPORATED BY REFERENCE None. | | | |
