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Organization and Operations - Additional Information (Detail) $ / shares in Units, $ in Millions				3 Months Ended	12 Months Ended
	Sep. 11, 2018 $ / shares shares	Aug. 14, 2018 USD ($) $ / shares shares	Aug. 08, 2018 shares	Dec. 31, 2018 USD ($) Daily_Departure State Air-craft City Employee Extension shares	Sep. 30, 2017 Air-craft Extension	Sep. 30, 2018 shares
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of states in which entity operates \| State				40
Number of aircrafts operated \| Air-craft				145
Number of cities in which entity operates \| City				121
Number of daily departures \| Daily_Departure				628
Number of employees \| Employee				3,400
Common stock, stock split				Effected a 2.5-for-1 stock split
Stock split ratio			2.5
Common stock, shares authorized			125,000,000	125,000,000		125,000,000
Preferred stock, shares authorized			5,000,000	5,000,000		5,000,000
Stock issued during period, shares, new issues	1,344,500
Common stock, warrants issued				10,614,990		10,614,990
Notice period for termination of agreement				The capacity purchase agreement is also subject to early termination for cause under specified circumstances and subject to the Company's right to cure under certain circumstances. United is also permitted, subject to certain conditions, to terminate the agreement early in its discretion by giving us notice of 90 days or more
Payment of lease cost \| $				$ 1.9
United [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of extension \| Extension				4	4
Renewal term extension period				2 years	2 years
Maximum [Member] \| United [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate extension period				8 years	8 years
CRJ-900 Aircraft [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated \| Air-craft				64
CRJ-700 Aircraft [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated \| Air-craft				20
CRJ-700 Aircraft [Member] \| Minimum [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Early termination right, expiration period				2019-08
CRJ-700 Aircraft [Member] \| Maximum [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Early termination right, expiration period				2019-12
E-175 Aircraft [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated \| Air-craft				60
E-175 Aircraft [Member] \| Mesa [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated \| Air-craft				18
E-175 Aircraft [Member] \| United [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated \| Air-craft				30	12
E-175 Aircraft [Member] \| Minimum [Member] \| Mesa [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Early termination right, expiration period				2028-01
E-175 Aircraft [Member] \| Minimum [Member] \| United [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Early termination right, expiration period				2019-06
E-175 Aircraft [Member] \| Maximum [Member] \| Mesa [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Early termination right, expiration period				2028-11
E-175 Aircraft [Member] \| Maximum [Member] \| United [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Early termination right, expiration period				2020-08
American Airlines Inc. [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Ownership interest				7.20%		7.20%
Restricted Stock [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of Shares, Granted				0
2018 Equity Incentive Plan [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Stock withheld to cover tax withholding requirements upon vesting to restricted stock units shares		314,198
Restricted stock, shares issued net of shares for tax withholdings		651,824
2018 Equity Incentive Plan [Member] \| Restricted Stock [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of Shares, Granted		1,266,034
Number of Shares, vested		966,022
2018 Equity Incentive Plan [Member] \| Restricted Stock [Member] \| Employees [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Additional restricted common stock shares issued		983,113
2011 and 2017 Plans [Member] \| Restricted Stock [Member] \| Employees [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Cancellation of common stock shares existing unvested restricted phantom units		491,915
Cancellation of common stock shares existing of unvested restricted stock		491,198
IPO [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Stock issued during period, shares, new issues		9,630,000
Shares issued, price per share \| $ / shares		$ 12.00
Gross proceeds of initial public offering \| $		$ 115.6		$ 124.2
Net proceeds from initial public offering \| $				111.7
Underwriting discounts and commissions \| $				8.7
Offering costs \| $				$ 3.8
Underwriter Options [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Common stock, warrants issued		1,444,500
Purchased Directly From Company [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Stock issued during period, shares, new issues	723,985
Purchased Directly From Selling Shareholders [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Stock issued during period, shares, new issues	620,515
Firm Shares and Option Shares [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Shares issued, price per share \| $ / shares	$ 12.00