A former employee of Boeing’s largest supplier has alleged that key aircraft parts regularly left the factory with serious defects. Santiago Paredes, who worked for Spirit AeroSystems in Kansas between 2010 and 2022, said he was used to finding “anywhere from 50 to 100, 200” defects on fuselages – the main body of the plane – that were being shipped to Boeing, and he felt threatened for raising his concerns. “I was finding a lot of missing fasteners, a lot of bent parts, sometimes even missing parts,” Paredes, who led a team of inspectors based at the end of the 737 Max production line, said in an interview with the BBC and theUS network CBS. “They just wanted the product shipped out. They weren’t focused on the consequences of shipping bad fuselages. They were just focused on meeting the quotas, meeting the schedule, meeting the budget … If the numbers looked good, the state of the fuselages didn’t really matter,” he alleged. Paredes said he regularly felt under pressure to be less rigorous during inspections, and was nicknamed “showstopper” for slowing down the production process by trying to tackle his concerns. “They always made a fuss about why I was finding it, why I was looking at it,” he said. Eventually a manager ordered him to change the way defects were reported in order to cut the number of concerns being logged. When he protested against the change, he said, he was demoted and moved to a different part of Spirit’s factory operations. “I felt I was being threatened, and I felt I was being retaliated against for raising concerns,” he said. It is the first time that Paredes, a former air force technician, has spoken publicly about his concerns. In January, Spirit and Boeing came under intense pressure after a mid-air blowout of a door panel on a Boeing 737 Max 9 that left a hole in the side of the plane. Investigators said the door had initially been fitted by Spirit and later removed by Boeing staff to deal with faulty parts. In 2018 and 2019, two 737 Max planes were involved in fatal crashes, which killed a total of 346 people. A Spirit AeroSystems spokesperson told the BBC the firm “strongly disagree[d]” with Paredes’s allegations, adding: “We are vigorously defending against his claims.” Boeing declined to comment. After his role was allegedly changed, Paredes filed an ethics complaint with the human resources department and wrote to Spirit’s chief executive saying he had “lost faith” and stressing it was his “last cry for help”. Paredes’s complaint was partially upheld, leading him to regain his leadership position and secure back pay. However, he left Spirit soon afterwards. His allegations have been included as testimony in a legal case filed by disgruntled Spirit shareholders who are accusing the company of trying to cover up serious and widespread quality failings. Spirit said it strongly disagreed with the allegations.