US government investigators say they’ve confirmed allegations federal aviation regulators allowed Southwest Airlines Co. to commit violations of safety rules involving repairs on planes it acquired from foreign carriers and the airline’s basic operations of them.

The Federal Aviation Administration and its parent agency, the Department of Transportation, agreed that multiple breaches occurred in how inspectors oversaw the Dallas-based carrier, according to findings released Wednesday by the Office of Special Counsel.

“I thank the whistle-blowers for raising these serious allegations about FAA’s oversight of Southwest Airlines,” Special Counsel Henry Kerner said in a press release. The OSC is the government’s chief agency for assessing whistle-blower complaints.

The FAA “took the Office of Special Counsel’s concerns seriously and acted quickly to adopt the recommendations that resulted from the investigation,” and is continuing work on outstanding issues, the agency said in a statement. 

Southwest said it had “cooperated fully” with multiple investigations related to the report since 2018. “As part of our emphasis on safety, we have maintained a transparent and professional relationship with the FAA,” the company said in an emailed statement. 

Many of the allegations have been reported previously and the FAA had earlier fined Southwest, but the OSC’s findings contain the final reports confirming those allegations and laying out the failures in detail.

According to FAA’s own review from April, which hasn’t previously been released, the failures included: allowing Southwest to fly 88 jets that were out of compliance, poor investigations into three Southwest accidents, mismanagement of a pilot-reporting program and allowing the carrier to violate weight-and-balance rules.