Federal investigators have claimed some safety inspectors who oversaw pilot training standards for the Boeing 737 Max were not qualified.
They also accused the Federal Aviation Administration of misleading Congress over the issue.
The probe was sparked from a whistleblower complaint that was passed to the U.S. Office of Special Counsel to investigate.
The FAA has vehemently denied the claims.
The investigation found that 16 out of 22 inspectors based in Seattle and Long Beach, California, did not fully complete their formal training, and 11 of these a flight-instructor license, which is mandatory for the post.
The FAA earlier told a Senate committee these employees did not work on writing training standards for the Max.
However, the Special Counsel investigation said this was not true based on the whistleblower account and other evidence collected during the investigation.
Special Counsel Henry Kerner wrote to lawmakres and President Trump stating the FAA ‘appear to have been misleading’ the government.
“The FAA’s failure to ensure safety inspector competency for these aircraft puts the flying public at risk,” Kerner wrote.
The FAA reiterated its stance, saying: “All of the aviation safety inspectors who participated in the evaluation of the Boeing 737 MAX were fully qualified for those activities.”