Matters came to a head for Mr Paredes personally, he claimed, when he was ordered by his manager to change the way in which defects were reported, in order to reduce their overall number.

After he protested, he said, he was demoted and removed to another part of the factory.

"I felt I was being threatened, and I felt I was being retaliated against for raising concerns," he said.

Mr Paredes subsequently filed an "ethics complaint" with the company's human resources department, and wrote to Spirit's then chief executive, Tom Gentile.

In that email, he said "I have lost faith on the quality organisation here at Spirit and this is my last cry for help".

He was subsequently reinstated in his leadership role and given back-pay after his complaint was partially upheld. He left the company soon afterwards.

His lawyers, Brian Knowles and Rob Turkewitz, said his story pointed to the "need for accountability and responsibility in the aviation industry".

"Aviation companies should encourage and incentivize those who raise such concerns and not retaliate against them', they added.

Mr Parades now maintains he would be reluctant to fly on a 737 Max, in case it still carried flaws that originated in the Wichita factory.

"I'd never met a lot of people who were scared of flying until I worked at Spirit," he said.

And then, being at Spirit, I met a lot of people who were afraid of flying - because they saw how they were building the fuselages."