Boeing said it will review the committee's report and said it has "cooperated extensively for the past year" with the investigation.

The report found that the Federal Aviation Administration 's review of the aircraft was "grossly insufficient" and that the agency "failed in its duty" to find safety problems.

Boeing 's 737 Max was "marred" by technical problems, a lack of transparency and other issues, according to the preliminary findings of a House investigation, released on Friday, into the beleaguered plane.

Rep. Peter DeFazio, an Oregon Democrat who heads the House committee, and Rep. Rick Larsen, a Democrat from Washington state, conducted the investigation and are planning to propose legislation this month that aims to ensure the FAA has more control over the certification process, DeFazio told CNBC this week.

The Max has been grounded for nearly a year after two crashes killed all 346 people aboard the two flights. Regulators have not said exactly when they expect to permit the jetliners to fly again but they are reviewing changes Boeing made to improve safety. A flight-control system Boeing included on the planes has been implicated in the two crashes.

The House Committee on Transportation and Infrastructure began probing in March 2019 — after the second of two Max crashes — how Boeing developed the planes and how regulators approved them three years ago. The crisis over the crashes resulted in the company's first annual loss since 1997, prompted it to suspend production and cost the former CEO his job last year. The planes are Boeing's bestselling aircraft.

The report was released just days before the one-year anniversary of the Ethiopian Airlines crash on March 10, 2019, the second of the two 737 Max crashes that occurred within five months of one another.

The FAA said it welcomed the House report. "While the FAA's certification processes are well-established and have consistently produced safe aircraft designs, we are a learning agency and welcome the scrutiny," it said in a statement. "We are confident that our openness to observations and recommendations will further bolster aviation safety worldwide."

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