The US Department of Transportation's Office of Inspector General has launched an investigation into the Federal Aviation Administration's handling of maintenance-related allegations against American Airlines and Allegiant Air.
American expresses surprise about the investigation, and Allegiant insists it operates to the highest safety levels.
"American Airlines was shocked to learn of the Office of Inspector General’s review and we stand by our strong safety record. Our team is working to understand why we are part of its review," the Fort Worth-based airline says in a statement.
"We welcome any analysis of our operation and safety culture," Las Vegas-based Allegiant says. "It will show what we know to be true: that Allegiant operates at the highest level of safety, in strict adherence with all FAA regulations and guidelines."
The DOT announced the review in a 9 May memo.
"Our objectives now are to assess FAA’s processes for investigating allegations of improper maintenance practices at… Allegiant Airlines and American Airlines," says the memo.
The agency will study the "FAA’s independent reviews, complaints to the FAA hotline and other sources to see whether inspectors conducting routine surveillance of Allegiant and American Airlines found similar discrepancies," it says.
Investigators will also asses "whether FAA ensures that Allegiant and American Airlines implement effective corrective actions to address the root causes of maintenance problems," it adds.
"We welcome the [Office of Inspector General's] examination of the FAA’s comprehensive oversight system," the FAA says. "This system is designed to identify potential risks before they become serious problems and ensure that corrective action is taken. The process is dynamic and requires that the FAA, and the airlines we oversee, constantly strive for safety improvements."
"The FAA is continually working to enhance safety for the flying public and is never content with the status quo," the agency adds.
The investigation stems from a review launched last year by the DOT inspector general to broadly assess the FAA's oversight of industrywide air carrier maintenance.
Investigators initially sought to assess how the FAA adjusts oversight in response to rapid airline expansion, cost cutting and mergers, according to the DOT's June 2017 announcement.
The early stages of that investigation revealed that the FAA shifted recently from stressing enforcement to "working with carriers to address the root causes for noncompliance", the DOT now says. The FAA has acknowledged that shift.
The early investigation also revealed differences in "relationships and information-sharing practices between air carriers and their FAA oversight officers".
Those findings and analyses of complaints to the FAA's hotline led the DOT in February to narrow its study to only focus on American and Allegiant.
The FAA has now shifted again – it will still study Allegiant and American, but will now focus specifically on the FAA's response to allegations of improper maintenance practices, the 9 May memo says.
The latest change comes after several lawmakers asked the DOT in April to examine issues, highlighted in recent media reports, related to the FAA's oversight of Allegiant, it adds.
Television programme 60 Minutes aired a story in April about Allegiant's maintenance and maintenance-related operational issues. Several other news outlets including FlightGlobal have written about maintenance-related issues at Allegiant.
Allegiant has repeatedly defended its maintenance practices and insisted it operates a safe airline. It said 60 Minutes presented a one-sided view and a "false narrative" about itself and the FAA.