Earnings Per Share - Calculations of Net Income/(Loss) Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2024	Mar. 31, 2023
Earnings Per Share And Equity [Abstract]
Net Income (Loss)	$ 11,660	$ (57,850)	$ (35,122)	$ (9,090)	$ (46,190)	$ (44,211)
Basic weighted average common shares outstanding	41,068		39,932		41,004	38,135
Diluted weighted average common shares outstanding	41,068		39,932		41,004	38,135
Net income/(loss) per common share attributable to Mesa Air Group:
Basic	$ 0.28		$ (0.88)		$ (1.13)	$ (1.16)
Diluted	$ 0.28		$ (0.88)		$ (1.13)	$ (1.16)