Federal safety officials are reviewing operations at Allegiant Air two years ahead of schedule, spurred by incidents including an aborted takeoff and a plane that landed low on fuel.
The Federal Aviation Administration routinely evaluates airlines every five years but moved up Allegiant's review from 2018.
This comes after an emergency landing at Phoenix-Mesa Gateway Airport Thursday night.
An FAA spokesman said Thursday that the agency is making sure that work Allegiant is doing "to address various internal issues has resulted in the desired improvements."
The review began in early April and is expected to run through June.
Allegiant said in a statement that it welcomed the review and FAA feedback.
"We have every confidence in our operation, and commit to sharing a summary of the FAA's review after it is concluded," the statement said.
The FAA sometimes moves up airline inspections because of management changes, labor disputes or other factors. The FAA said the decision to speed the Allegiant review was based partly on two incidents last year.
In one, a mechanical failure was blamed for causing the nose of the plane to rise too soon during takeoff. Pilots aborted the takeoff on the runway in Las Vegas.
In the other, a plane flown by two Allegiant executives with airline-pilot licenses ran low on fuel and made an emergency landing at a closed airport in Fargo, North Dakota. The FAA closed the case after Allegiant took steps to improve training and procedures.
The airline has suffered other high-profile breakdowns and emergency landings, including an engine fire that caused pilots to abort another Las Vegas flight.
The president of the union representing Allegiant's pilots said the early FAA review underscores the airline's problems with maintenance.
"It's clear that Allegiant's bare-minimum approach to its operation isn't working," said Dan Wells, president of Teamsters Local 1224.
The FAA decision to move up the Allegiant review was previously reported by the Tampa Bay Times.
Allegiant Air is a unit of Las Vegas-based Allegiant Travel Co.