Congressional investigators blamed two deadly Boeing 737 MAX crashes on "repeated and serious failures" by Boeing and air safety regulators, according to a report released on Wednesday. 

The 239-page report released by congressional Democrats flagged numerous failings, including pressure in Boeing to rush the MAX out in order to compete with an Airbus plane, a "culture of concealment" in which the planemaker withheld key information from regulators and undue influence by the company on Federal Aviation Administration (FAA) higher-ups that marred oversight.

The report is the culmination of an 18-month probe by the House Transportation and Infrastructure Committee into crashes of Lion Air and Ethiopian Airlines planes that together claimed 346 lives.

"Our report lays out disturbing revelations about how Boeing – under pressure to compete with Airbus and deliver profits for Wall Street – escaped scrutiny from the FAA, withheld critical information from pilots and ultimately put planes into service that killed 346 innocent people," said Chairman Representative Peter DeFazio, an Oregon Democrat.

"What's particularly infuriating is how Boeing and FAA both gambled with public safety in the critical time period between the two crashes."

The report adds to scrutiny of both Boeing and the FAA as the agency manages the process of requiring upgrades to the plane before it is cleared to fly again. The MAX has been grounded since March 2019.

In a statement, Boeing said it "learned many hard lessons as a company from the accidents ... and from the mistakes we have made." 

"As this report recognizes, we have made fundamental changes to our company as a result, and continue to look for ways to improve," it added.

"Once the FAA and other regulators have determined the MAX can safely return to service, it will be one of the most thoroughly scrutinized aircraft in history, and we have full confidence in its safety."

An FAA spokesman said the agency "is committed to continually advancing aviation safety and looks forward to working with the committee to implement improvements identified in its report."

The spokesman added that "the FAA continues to follow a thorough process, not a prescribed timeline, for returning the aircraft to service."

The report said Boeing made "faulty design and performance assumptions" especially surrounding a key safety system called MCAS, which was linked to both the Lion Air and Ethiopian Airlines crashes.

MCAS, which was designed to help counter a tendency of the MAX to pitch up, could activate after data from only a single sensor.

The report criticized Boeing for withholding "crucial information from the FAA, its customers, and 737 MAX pilots," including "concealing the very existence of MCAS from 737 MAX pilots."

FAA is requiring a number of new safeguards to MCAS, including requiring it to receive data from two sensors, before it allows the MAX to return to service.

The report cited instances where Boeing employees granted permission to represent interests of the FAA "failed to disclose important information to the FAA that could have enhanced the safety of the 737 MAX."

Boeing did not disclose the existence of MCAS in crew manuals and sought to convince regulators not to require more expensive simulator training for MAX pilots. In January, Boeing agreed to back simulator training before pilots resume flights.

The report said the FAA "failed to ensure the safety of the travelling public."

Lawmakers have proposed numerous reforms to restructure how the FAA oversees airplane certification. A Senate committee will take up a reform bill on Wednesday.

Lawmakers suggested Boeing was motivated to cut costs and move quickly to get the 737 MAX to market.

"This is a tragedy that never should have happened," DeFazio told reporters. "We're going to take steps in our legislation to see that it never happens again as we reform the system."