A former employee at Boeing, Johna Barnett who was known for raising concerns about the firm's production standard was found dead in the United States, reported BBC.
Barnett, 62, who worked for Boeing for 32 years until his retirement in 2017, died from a "self-inflicted" wound on March 9 and police were investigating the matter.
The whistlerblower worked for the US plane giant for 32 years until his retirement in 2017 on health grounds, the BBC report added.
He has been giving evidence in a whistlebower lawsuit against the company in the days before his death.
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He worked as a quality manager at the North Charleston plane from 2010 making the 787 dreamliner, a state-of-the-art airliner used mainly for long-haul routes.
In 2019, he told the BBC that the under-pressure workers were purposely fitting sub-standard parts to aircraft on production line.
Barnett also said that he got to know about a serious problems with oxygen systems, which could mean that one in four breathing masks won't work in an emergency.
As per the BBC report, Barnett said that soon after starting his work in South Carolina he has become concerned that the push to build new aircraft meant that assembly was rushed and safety was compromised.
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While the company has denied such claims, a review by the US regulator the Federal Aviation Administration (FAA) in 2017, upheld some of Barnett's concerns.
The FAA establised that the location of at least 53 "non-confirming" parts in the factory was unknown and they were considered lost. The regulator ordered Boeing to take remedial action.
On the issue of oxygen cylinders, the company said that in 2017, it had "identified some oxygen bottles received from the supplier that were not deploying properly".
But the airplane maker denied that any of them were actually fitted on aircraft.