The US Department of Transportation (DOT) has ordered the Federal Aviation Administration (FAA) to tighten its safety oversight of Allegiant Air (G4, Las Vegas Harry Reid), Reuters has said citing a confidential report by the DOT.

According to the report, the DOT Inspector General found that FAA inspectors had incorrectly documented and assessed 36 in-flight engine shutdowns related to Allegiant Air's McDonnell Douglas jets. A total of nine recommendations aimed at improving checks and balances were ordered of which the FAA said it agreed with eight and partially agreed with the ninth.

"Safety has always been - and will remain - at the heart of our operation, and fundamental to everything we do. We vehemently dispute any implications to the contrary. We continue to work with the FAA and other regulatory agencies to ensure we meet and exceed all Federal standards, and plan our future with complete commitment to vigilant monitoring and continuous improvement," Allegiant Air said in a statement to ch-aviation.

The carrier also underlined that the report centred "upon work with the FAA which occurred years ago, involving an aircraft type since retired from Allegiant’s fleet".

The investigation was launched in May 2018 after a series of in-flight engine shutdowns and other engine-related incidents. The relatively frequent incidents continued until the airline retired its last MD-80 aircraft later in 2018. According to the report, the FAA failed to adequately track engine shutdown risks after 21 incidents between 2014 and 2018.

The DOT further criticised the handling of a failure related to a maintenance provider servicing the carrier's engines. As a result of a 2015 failure of the provider to install a cotter pin on an aircraft, the FAA inspectors initially proposed to suspend the provider's licence. However, the agency's regional offices later changed the penalty to compliance action and closed six out of eight proceedings before ensuring that any corrective measures had been properly taken.

Allegiant had not responded for a request for comment by the time of going to press.

According to the ch-aviation fleets module, after the retirement of all MD-80s, Allegiant Air now operates thirty-eight A319-100s and sixty-six A320-200s.