Boeing refused to discard faulty parts which could have been used in newly built aircraft, resulting in a “catastrophic event”, a whistleblower has claimed.

Sam Mohawk, a quality assurance inspector, told lawmakers he was being pressured by the company to conceal evidence from the regulator that speaks to allegations of bad practices, according to a Senate report.

The fresh allegations were released hours before Dave Calhoun, Boeing chief executive, faced a grilling from US senators on Tuesday over the company’s safety culture.

It marks the first time Mr Calhoun has testified in front of lawmakers after a door plug blew off an Alaska Airlines 737 Max flight on Jan 5, leaving a gaping hole in its side.

Mr Calhoun said Boeing was “accountable for what happened”.

Richard Blumenthal, the chairman of the Senate panel, said that Mr Mohawk had been threatened with termination for speaking out.

“This is a culture that continues to prioritise profits, push limits, and disregard its workers.”

“A culture that enables retaliation against those who do not submit to the bottom line. A culture that desperately needs to be repaired.”

Since the Alaska Airlines incident, a string of whistleblowers, including Sam Salehpour, a current engineer at Boeing, and Roy Irvin, a former quality investigator, have raised safety concerns.

During the hearing, Mr Blumenthal said a dozen whistleblowers had come forward.

“It is a moment of reckoning, and an opportunity to change a broken safety culture”, Mr Blumenthal said.

Mr Mohawk, who works at the Boeing 737 factory in Renton, Washington, recently told the panel he had witnessed mishandling of faulty parts.

He alleged the firm was cutting corners and losing track of parts that had been labelled as non-conforming, or not up to design standards, according to Mr Blumenthal.

There was a risk these parts made it in the aircraft because they were sometimes fixed or mislabeled when they should have been discarded

He said he “feared” the parts “were being installed on the 737s and that it could lead to a catastrophic event”, the report read.

“Mohawk has also alleged that he has been told by his supervisors to conceal evidence from the FAA, and that he is being retaliated against as result,” according to a statement from the Senate Homeland Security’s permanent subcommittee on investigations.

Mr Blumenthal called the allegations “chilling”.

“This is not an industry where it’s OK to cut corners, to reduce inspections, to take shortcuts and rely on broken parts that happen to be sitting around”, he said.

Boeing said it is reviewing the claims it heard about on Monday.

“We continuously encourage employees to report all concerns as our priority is to ensure the safety of our airplanes and the flying public”, it said.

Boeing also said it has increased the size of its quality team and “increased the number of inspections per airplane significantly since 2019”.

Mr Calhoun, who said he would step down before the end of the year amid scrutiny of the firm, was expected to acknowledge the firm’s shortcomings during his appearance.

“Our culture is far from perfect, but we are taking action and making progress,” Mr Calhoun told the committee.

Mr Calhoun said he had not directly spoken to any of the Boeing whistleblowers

He said some Boeing employees had been fired for retaliating against whistleblowers, but could not say how many.

‘Moment of reckoning’

Mr Blumenthal called the hearing a “moment of reckoning” for Boeing.

Zipporah Kuria’s father Joseph Waithaka, 55, died in the Ethiopian Airlines crash in 2019.

She was one of several family members whose family had died in Boeing accidents demonstrating in Washington ahead of the hearing

“My being here so that Calhoun can see my father’s face and the cost of his decision.”

“We’re living in a world where people pay with their lives and people profit and governments and congress and FAA, people just look aside.... We have been a muffled scream that has been screaming and no one has been paying attention. I don’t want to say that this hearing doesn’t mean much but I really hope he can face what he has done.”

Since the January blowout scrutiny of the planemaker by regulators and airlines has intensified.

The National Transportation Safety Board said four key bolts were missing from the Alaska Airlines plane. The Justice Department has opened a criminal investigation into the incident.