Two fatal crashes of Boeing 737 Max aircraft were partly due to the plane-maker’s unwillingness to share technical details, a congressional investigation has found.
The US report is highly critical of both Boeing and the regulator, the Federal Aviation Authority (FAA).
It blames a “culture of concealment” at Boeing, but says the regulatory system was also “fundamentally flawed”.
Boeing said it had “learned many hard lessons” from the accidents.
“Boeing failed in its design and development of the Max, and the FAA failed in its oversight of Boeing and its certification of the aircraft,” the 18-month investigation concluded.
The Boeing 737 Max has been grounded since March 2019 after two crashes, in Indonesia and Ethiopia, caused the deaths of 346 people.
The nearly 250-page report found a series of failures in the plane’s design, combined with “regulatory capture”, an overly close relationship between Boeing and the federal regulator, which compromised the process of gaining safety certification.
“[The crashes] were the horrific culmination of a series of faulty technical assumptions by Boeing’s engineers, a lack of transparency on the part of Boeing’s management, and grossly insufficient oversight by the FAA.”
Boeing said it had made “fundamental changes” to the company as a result of the accidents.
The FAA said it would work with lawmakers to “implement improvements identified in the report”.
The report said Boeing had failed to share information about a key safety system, called MCAS, designed to automatically counter a tendency in the 737 Max to pitch upwards. Boeing was at fault for “concealing the very existence of MCAS from 737 pilots”, it found.
MCAS was not in crew manuals and Boeing sought to convince regulators not to require simulator training for Max pilots, which would incur extra costs.
The MCAS system has been blamed for both crashes that came within months of each other, shortly after the plane went into operation.