A former quality inspector for Spirit AeroSystems claims he found many defects on parts due for shipping.
Fuselages made by Boeing's largest supplier regularly left the factory with serious defects, according to a former quality inspector at the firm.
Santiago Paredes who worked for Spirit AeroSystems in Kansas, told the BBC he often found up to 200 defects on parts being readied for shipping to Boeing.
He was nicknamed "showstopper" for slowing down production when he tried to tackle his concerns, he claimed.
Mr Paredes made the allegations against Spirit in an exclusive interview with the BBC and the American network CBS, in which he described what he said he experienced while working at the firm between 2010 and 2022.
He was accustomed to finding "anywhere from 50 to 100, 200" defects on fuselages - the main body of the plane - that were due to be shipped to Boeing, he said.
"I was finding a lot of missing fasteners, a lot of bent parts, sometimes even missing parts."
If I was a Boeing whistleblower I would be live streaming my life, mentioning every hour that I feel fine and not suicidal, and hiring someone for minimum wage to just hangout with me every night with the only job to call 911 if something happens