Boeing quality engineer Sam Salehpour’s managers at Boeing retaliated against him and quashed safety concerns he raised over malfunctioning aircraft parts, he told a Senate hearing on Boeing’s safety culture Wednesday.

A Boeing engineer for over 30 years, Salehpour testified that he tried to warn personnel of safety issues over the course of three years, including writing memos that reached the desks of Mark Stockton, senior director for 787 engineering, and Lisa Fahl, a vice president of the company. Instead of addressing his concerns, he said, Boeing brass shut him down, part of a broader trend within the company of brushing off safety concerns in the name of productivity and the bottom line.

“I was ignored. I was told not to create delays,” he said. “I was told, frankly, to shut up.”

Democratic Sen. Richard Blumenthal of Connecticut called the hearing led by the Homeland and Governmental Affairs subcommittee after a Boeing 737 Max 9 aircraft door plug flew off an Alaska Airlines plane midflight on Jan. 5. Since then, numerous Boeing planes have experienced safety mishaps. A Federal Aviation Administration probe completed in March found Boeing failed 33 of 89 product audits and noted “dozens of problems” at its facilities. Boeing’s safety incidents have rippled across the aviation industry: United Airlines reported a $142 million net loss in its first quarter after the 737 Max was grounded, with CEO Scott Kirby blaming the weak quarter on Boeing’s mishap.

Blumenthal said the April 17 hearing will be the first of many to rectify the safety oversights at Boeing. No Boeing personnel, including CEO Dave Calhoun, attended the hearing, though they are cooperating, a company spokesperson told AP. Boeing did not respond to Fortune’s request for comment.

Those who testified in the Wednesday hearing—a series of Boeing and FAA personnel, including Salehpour—made clear their belief that many of Boeing’s safety misfires would have been avoided if greater care was put into listening to employee apprehensions over aircraft quality.

“My boss said, ‘I would have killed someone who said what you said in a meeting,’” Salehpour said in his testimony. “This is not a safety culture when you get threatened for bringing [up] issues of safety concerns.”

Like bending a paperclip

Salehpour said witnessed shoddy engineering that could endanger the safety of Boeing passengers during his time as quality engineer. He noticed gaps between aircraft panels were not properly shimmed, or filled, leaving creases for debris to fall into. The gaps were a result of pieces not naturally fitting together, but rather being jammed and finagled with “excessive force” that added stress to components that could cause long-term damage.

“I literally saw people jumping on the pieces of the airplane to get them to align—I called it the Tarzan effect,” he said in his testimony.

Salehpour likened the stress added to these roughly manipulated parts to bending a paper clip: The clip isn’t initially damaged when bent a couple times, but after enough manipulation, the thin metal eventually snaps.

When Salehpour consulted inspection documentation, it confirmed what he saw firsthand: Of Boeing’s 29 inspected 787 aircrafts, 98.7% had gaps in the fuselage that exceeded specifications, Salehpour said.

“Effectively, they are putting out defective airplanes,” he said.

Salehpour’s repeated warnings about aircraft quality got him moved from the 787 division to the 777 division of the company, he said: a process that entailed his boss first not inviting him to team meetings, then offering him a “new job” in a different department.

“They do it pretty stealthily,” he said.

3:00 a.m. nightmares and punctured tires

The consequences of speaking out against an aviation juggernaut bubbled to the surface recently after whistleblower John Barnett died by suicide in March. The former Boeing quality manager revealed the shoddy practices in North Charleston, S.C., in 2019, shortly after the two tragic Boeing crashes.

The backlash Salehpour experienced for speaking out took a personal toll on him. Though he is still a Boeing employee, it’s only because his lawyer went through the Whistleblower Protection Program.

Salehpour said that after he spoke out, his boss started calling his personal number to berate him for 40 minutes at a time, as well as canceling doctor’s appointments on his email calendar. One day Salehpour found a nail caught in one of his car’s new tires. When he took it to the shop, the mechanic told him he didn’t pick up the nail from normal driving—it was likely deliberately put there. Though Salehpour believes the incident happened while he was at work, he has no proof.

As a result of the fallout, Salehpour said, he has woken up at 3 a.m. to nightmares of being stabbed.

“This is the hell that I was subjected to,” he said. “I’m still receiving psychological help to just get back to normal.”