Days before the anniversary of the Ethiopian Airlines crash that killed 157, a US congressional committee promised to tighten oversight of Boeing

Boeing made missteps and withheld information about the 737 MAX while federal regulators failed to provide proper oversight, leading to a "fundamentally flawed" aircraft that demands tighter rules, a US congressional committee said Friday.

The preliminary report from the House Transportation Committee blasts Boeing management and the Federal Aviation Administration and calls for reforms.

"The fact that multiple technical design missteps or certification blunders were deemed 'compliant' by the FAA points to a critical need for legislative and regulatory reforms," the report said, calling the aircraft "fundamentally flawed and unsafe."

The Democratic committee chair plans to introduce legislation to address the failings in coming weeks, according to a statement from the committee.

Released days before the anniversary of the crash of an Ethiopian Airlines MAX, the second involving the model, the report cited a list of failings, including Boeing management brushing off concerns of engineers, and FAA officials ignoring warnings from its own experts.

The congressional investigation aimed "to better understand how the system failed so horribly," committee Chair Peter DeFazio said in a statement.

And he said the committee intends to continue its investigation "to bring into focus the multiple factors that allowed an unairworthy airplane to be put into service, leading to the tragic and avoidable deaths of 346 people."

The MAX has been grounded worldwide since the accident, which happened a few months after the Lion Air tragedy in Indonesia in October 2018.

"Both Boeing and the FAA gambled with the public's safety in the aftermath of the Lion Air crash," the report said.

'Grossly insufficient' oversight

Many of the flaws in design and oversight had been revealed over the months since the second crash, but the damning report lays them out one after the other.

A congressional investigation found "grossly insufficient" oversight of the Boeing 737 MAX, and executives who dismissed safety concerns of the company's own engineers

The report describes Boeing's "fundamentally flawed assumptions" about technology in the plane, including the flight software at the epicenter of both tragedies: the MCAS.

And the company has a "culture of concealment" that meant "it withheld crucial information" including from pilots, customers and the FAA.

Senior Boeing leadership "rebuffed concerns" of a plant supervisor about the production pressures and the impact on safety, who called for a temporary halt to the manufacturing to address the issues.

"Despite those warnings, Boeing ramped up production instead."

Regulators, meanwhile, exercised "grossly insufficient" review and had a relationship with Boeing that created "inherent conflicts of interest that have jeopardized the safety of the flying public."

"At times, FAA management has undercut the authority and judgment of its own technical experts and sided with Boeing," the report said.

"The FAA failed to fully exercise its safety oversight authority. The agency did not ask enough questions or scrutinize sufficiently."

The FAA responded to the report saying it will "welcome the scrutiny" from the and the investigations into the two accidents "will be a springboard to an even greater level of safety."

However, late Friday, the FAA announced a proposed $19.7 million fine against Boeing for certifying the MAX and its predecessor the 737 NG as airworthy when they contained sensors that were not "tested and approved as compatible" with the installed flight systems.

Boeing presented "791 aircraft for airworthiness certification when the aircraft were unairworthy," the FAA said in a letter to the company.

In a statement addressing the congressional finding, Boeing said, "We have cooperated extensively for the past year with the Committee's investigation. We will review this ."