The US Federal Aviation Administration's recertification testing of the Boeing 737 Max was "inappropriately influenced" by the Chicago-based plane maker, according to a US Senate report.
The 102-page report, based on whistleblower information and FAA staff interviews, found that Boeing officials had “inappropriately coached” test pilots during simulations to test their reactions to a failure in the flight control system known as MCAS.
The MCAS flight control system was to blame in the two 737 Max crashes that killed 346 people.
“The committee concludes FAA and Boeing officials involved in the conduct of this test had established a pre-determined outcome to reaffirm a long-held human factor assumption related to pilot reaction time to a runaway stabiliser,” the report said.
“It appears, in this instance, FAA and Boeing were attempting to cover up important information that may have contributed to the 737 MAX tragedies.”
The report was released by the Senate Committee on Commerce, Science and Transportation came after an investigation into the FAA that began in April 2019, weeks after the 737 Max second crash, when it began receiving information from whistleblowers.
"Our findings are troubling," Republican Senator Roger Wicker, chairman of the Senate Committee, said.
"The report details a number of significant examples of lapses in aviation safety oversight and failed leadership in the FAA. It is clear that the agency requires consistent oversight to ensure their work to protect the flying public is executed fully and correctly.”
Last month, the FAA approved the 737 Max's return to commercial service, ending a 20-month ban. Brazil’s Gol Linhas Aereas Inteligentes became the first airline to resume flights.
The FAA said on Friday that it was “carefully reviewing the document, which the committee acknowledges contains a number of unsubstantiated allegations”.
The agency also said it was confident that the safety issues responsible for crashes involving Lion Air Flight 610 and Ethiopian Airlines Flight 302 had been addressed "through the design changes required and independently approved by the FAA and its partners”.
Boeing said on Friday that it remained “committed to improving aviation safety, strengthening our safety culture and rebuilding trust with our customers, regulators, and the flying public".
The plane maker said it would take the committee’s findings serioulsy and continue to review the report in full.
“We have learnt many hard lessons from the Lion Air Flight 610 and Ethiopian Flight 302 accidents, and we will never forget the lives lost on board,” Boeing said.
“The events and lessons learnt have reshaped our company and further focused our attention on our core values of safety, quality and integrity.”
The report said that over the past 20 months, committee staff had received information from several whistleblowers who alleged “cosiness between the FAA and Boeing, and lack of diligent oversight by the FAA in general, specifically in the certification of the 737 Max”.
The whistleblowers also alleged that Boeing had intentionally misled FAA certification efforts and downplayed the significance of the role MCAS played in the crashes, the report said.
In its other findings, the report said the FAA continued to retaliate against whistleblowers instead of welcoming their disclosures in the interest of safety.