John Barnett, a former Boeing employee and whistleblower, was found dead from a self-inflicted wound.
He worked for Boeing for 32 years and raised concerns about production standards and safety compromises at the company.
Barnett had been giving evidence in a lawsuit against Boeing, alleging pressure on workers led to sub-standard parts being used in aircraft.
The FAA had upheld some of his concerns.
His death coincides with ongoing scrutiny of Boeing's production standards, including a recent incident with a Boeing 737 Max.
