Recertification of the redesigned Boeing 737 Max jetliner — set to fly again soon from the United States after two tragedies over the past three years — was marred by "lapses in aviation safety oversight," warns a US Senate committee report.

The plane, already back in service in Brazil, was recently given the approval to resume US domestic flights late in December after software upgrades and additional pilot training.

Blamed in those tragedies was an automated flight control system, called MCAS, which sent both planes into fatal nose-down dives in Indonesia and Ethiopia, killing 346 occupants.

Releasing his panel's report Friday, US Senate Commerce Committee chairman, Republican Roger Wicker blamed both the US aviation regulator, the Federal Aviation Administration and the planemaker for failures during the recertification process.

Wicker said the report detailed "a number of significant examples of lapses in aviation safety oversight and failed leadership in the FAA," over its review of the safety of the 737 Max jet.

The FAA had continued to retaliate against whistleblowers and during post-crash recertification, Boeing officials present had "inappropriately" influenced test pilots, the Senate panel found.

However, the FAA said the report "contains a number of unsubstantiated allegations" and defended its review of the Max, calling it thorough and deliberate.

'Pre-determined outcome'

The Wicker panel report also accuses the FAA and Boeing officials of establishing a "pre-determined outcome to reaffirm a long-held human factor assumption related to pilot reaction time."

Corroborated, said the committee, had been the account of a whistleblower who alleged Boeing officials encourage test pilots to "remember, get right on that pickle switch" prior to a nose-down exercise that resulted in reaction times of about four seconds and, in another case, 16 seconds.

The reaction of three flight crews in simulator tests, while Boeing representatives watched, was still slower than the aircraft manufacturer assumed, said the report.

Each time, the plane would have been thrown into a nose-down pitch, although recovery would still have been possible, investigators said.

Legislation is pending to make changes to the FAA's certification process for new planes — submitted by chair Wicker and the panel's top Democrat Maria Cantwell.

"It is clear that the [FAA] agency requires consistent oversight to ensure their work to protect the flying public is executed fully and correctly," concluded the panel.

In its response to the report, Boeing said it took "seriously the committee's findings and will continue to review the report in full."

ipj/mm (AP, Reuters, AFP)