By Micah Maidenberg

An audit by the U.S. Transportation Department's inspector general has concluded federal air-safety regulators are falling short in monitoring maintenance practices at American Airlines Group Inc.

The Federal Aviation Administration's oversight controls haven't been strong enough to ensure American Airlines' maintenance fixes addressed root causes of problems, according to a copy of the report posted on the inspector general's website.

In 2015, the FAA initiated an effort meant to ensure inspectors were focusing on the underlying causes of aviation-safety problems, according to the report. The inspector general's audit of American's maintenance practices began three years later following a request by members of the U.S. House Transportation Committee. The agency is still refining the guidance it gives inspectors, according to the report.

The inspector general's office, led by Eric Soskin, said that in 92% of the 185 cases it sampled between March 2016 and March 2020, FAA inspectors accepted American's determinations of the problems' underlying causes that didn't actually identify what led to the lapses.

The FAA also closed out its compliance actions before the carrier took corrective measures and the agency could check them, according to the inspector general's report.

American, the largest carrier globally, hasn't had a fatal accident in nearly two decades, the report said. The report from the inspector general's office said that figuring out why problems occur, and not just focusing on mistakes by individuals, is important for improving aviation safety.

A spokeswoman for American said the safety of customers and employees guides the airline's decisions, and that American welcomed the inspector general's report. "We plan to work with the FAA to ensure we take positive action and continuously refine and improve our safety controls," she said.

The FAA said that it agrees with many of the recommendations from the inspector general and is taking steps to address them. The agency has identified many of the same issues in the course of its regular oversight work, according to a person familiar with the FAA.

The agency plans to beef up training, among other efforts, according to a memo from the FAA included in the report.

The review also scrutinized how the FAA evaluates American's safety efforts, and whether the agency is sufficiently policing risks.

For example, American once miscategorized the safety risk of an airplane's emergency escape slide that didn't work, according to the report. It was given a moderate risk rating. But had the inoperable slide been designated as serious, it might have led to a higher-level response from company management, the report said.

American reported the issue with the slide to the FAA after discovering a vendor had left behind a tool, the company spokeswoman said. Following the inspection, she said, the vendor fixed its process.

The Transportation Department inspector general's office declined to comment.

--Andrew Tangel contributed to this article.

Write to Micah Maidenberg at micah.maidenberg@wsj.com

(END) Dow Jones Newswires

10-22-21 1124ET