Peter DeFazio, who chaired the House Transportation and Infrastructure Committee until 2022, said the focus needs to turn to Spirit AeroSystems, which built the door plug that blew out of the Alaska Airlines plane after it took off on 5 January.

Mr DeFazio said on Tuesday that Boeing has been "happy with the crappy stuff from Spirit because it's cheap".

He previously led an investigation into Boeing after all of its MAX passenger jets were grounded in March 2019 for 20 months following two crashes in Ethiopia and Indonesia which killed 346 people between them.

Boeing chief executive Dave Calhoun has acknowledged the company made a mistake after six crew members were injured on flight 1282 from Portland to California on 5 January.

In his first public comments on the incident, Mr Calhoun told staff it would work with regulators to make sure it "can never happen again".

His comments come after both Alaska Airlines and United Airlines - two of the US carriers that fly the 737-9 - reported finding loose bolts and other hardware in other planes, suggesting issues with the door plugs are not limited to one plane.

"We're going to approach this number one acknowledging our mistake," Mr Calhoun told employees, according to an excerpt released by Boeing.

"We're going to approach it with 100% and complete transparency every step of the way."

Shortly after Alaska Airlines flight 1282 had taken off a window and chunk of fuselage blew out of the plane.

It is believed roller guides at the top of one of the door plugs broke (for reasons unknown). This allowed the entire panel to swing upward and break away, leaving six people injured.

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The US National Transportation Safety Board said on Tuesday that it was investigating whether four bolts that help prevent the panel from sliding up on rollers were missing when the plane took off from Portland or whether they blew off "during the violent, explosive decompression event".

Boeing executives told staff the issues were being treated as a "quality control issue" and checks are under way at Boeing and Spirit.

On Monday, Spirit said in a statement that "quality and product integrity" are a priority. It said: "Spirit is a committed partner with Boeing on the 737 programme, and we continue to work together with them on this matter."

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Meanwhile, Mr Calhoun said Boeing employees will "ensure every next plane that moves into the sky is in fact safe".

It comes after the White House said on Tuesday that Americans should feel safe flying in the wake of the incident.

The Federal Aviation Agency continues to inspect each 737-9 before an "airworthiness certificate is issued and cleared for delivery".