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An aircraft mechanic who was contracted to repair Boeing planes has alleged he was labelled a "snitch" and then sacked for speaking up over safety concerns.
Richard Cuevas claimed he witnessed substandard manufacturing and maintenance work on a crucial section of Boeing 787 aircraft.
Boeing, which has been dogged by questions over whether its safety culture is rigorous enough, said the issues had been investigated and "did not present a safety concern".
Lawyers representing Mr Cuevas alleged he reported critical issues that could create a serious public safety risk and has filed complaints with the Federal Aviation Administration and the Occupational Health and Safety Administration.
Mr Cuevas, who has worked in the aviation industry for 40 years, was contracted to Spirit Aerosystems, to work on Boeing's 787 forward pressure bulkhead, a dome at the nose of the aircraft which serves as a barrier.
“He recognised the substandard work and expressed concern," Mr Cuevas' lawyers said. "But Spirit and Boeing failed to stop the faulty manufacturing processes."
According to the legal filings a colleague then remarked: “We’ve got a snitch among us.”
Mr Cuevas said he was sacked by Spirit Aerosystems in March 2024.
Boeing told the BBC: “A subcontractor’s employee previously reported concerns to us that we thoroughly investigated, as we take seriously any safety-related matter."
However, the issues raised were found not to present a safety concern and had been addressed, Boeing said.
Spirit Aerosystems spokesperson Joe Buccino, said the firm was "looking into the matter".
"We encourage all Spirit employees with concerns to come forward, safe in knowing they will be protected,” he said.
Mr Cuevas' lawyers Debra Katz and Lisa Banks have previously represented another Boeing whistleblower, Sam Salehpour, who earlier this year told US Congress he had been harassed and threatened after he alleged there were quality problems at Boeing.
Mr Salehpour's concerns were also focused on production of the Boeing 787 model.
That is a different model to the 737 Max which was involved in mid-air cabin blow out in January.
That incident prompted heightened scrutiny of Boeing's safety standards.
In April, Boeing said that it had seen a sharp increase in employees speaking up after it gave assurances there would be no retaliation for doing so.
Boeing said that signalled progress towards "a robust reporting culture".
"We continue to put safety and quality above all else and share information transparently with our regulator, customers and other stakeholders," the company said.