Washington DC CNN  —  Boeing’s already battered reputation took another hit at two Senate committee hearings Wednesday on Capitol Hill, with witnesses questioning how the company builds airplanes and the safety of those planes. One of the key witnesses was Boeing engineer Sam Salehpour, a whistleblower who said he’s been threatened for bringing safety concerns to his managers over several years, but that he was testifying due to his belief that “they are putting out defective airplanes.” “I have serious concerns about the safety of the 787 and 777 aircraft and I’m willing to take on professional risk to talk about them,” he said in his opening statement. He said when he raised concerns, “I was ignored. I was told not to create delays. I was told, frankly, to shut up.” He said that Boeing used “unmeasured and unlimited” amount of force – including people jumping on pieces of the airplane – to correct misalignment between sections of jets, and that the gap ended up being much more than the 5/1000th of an inch allowed by Boeing’s own standards. Boeing did not have any witnesses at either hearing Wednesday, but at a briefing earlier this week it defended the standards used to build planes. It said the 5/1000th of a inch gap is only the width of a human hair or two pieces of paper, and was a “hyper-conservative” standard. It said even when the gap is wider than what was originally proscribed, inspections of the jets showed no signs of fatigue or other problems even after years in service. But Salehpour said that Boeing’s assurances are invalid. “When operating at 35,000 feet, the size of a human hair can be a matter of life and death,” he said. “I have a very negative attitude toward the safety culture,” he said later in the hearing. “When I bring something to my boss, he prevents me from even documenting or sending information. When a quality manager says don’t send to a subject matter to an expert… that’s concerning.” Another witness, Ed Pierson, a former Boeing manager and the executive director of The Foundation for Aviation Safety, said the lack of paperwork that has been provided to National Transportation Safety Board investigators after a door plug blew out of a Boeing 737 Max flight by Alaska Airlines in January amounted to “a criminal cover-up.” “Records do exist documenting in detail the hectic work done on the Alaska Airlines airplane and Boeing’s corporate leaders know it too, because they fought to withhold these same damning records after the two Max crashes,” he said in his opening comments. But Boeing has yet to provide documentation to federal investigators of which employees worked on the door plug that blew off the Alaska Air flight due to it missing four bolts needed to hold the plug in place. Boeing recently said it has searched for records but believes its employees did not document the work. Senators on both sides of the aisle expressed concerns about the testimony. “This story is serious, even shocking,” said Democratic Sen. Richard Blumenthal of Connecticut, the chairman of the Senate permanent subcommittee on investigations. “There are mounting, serious allegations that Boeing has a broken safety culture, and a set of practices that are unacceptable.” Boeing Quality Engineer Sam Salehpour prepares to testify during the Senate Homeland Security and Governmental Affairs Subcommittee on Investigations hearing to examine Boeing's broken safety culture in the Dirksen Senate Office Building on Wednesday, April 17, 2024. Bill Clark/CQ Roll Call/Sipa He said that since the hearing was announced, his committee has heard from other whistleblowers inside of Boeing. He said one mechanic from its nonunion South Carolina factory wrote that when he brought concerns, he was “told that hundreds of others were waiting outside the gates for our jobs.” “Boeing is at a moment of reckoning,” Blumenthal said. “It’s a moment many years in the making. It’s a moment that results not from one incident or one flight or one plane.” At its briefing on Monday ahead of the hearing Boeing said it has encouraged employees to bring forward safety concerns and since the Alaska air incident they have been doing so in much greater numbers. But ranking committee member Republican Sen. Ron Johnson of Wisconsin said that while “we all want Boeing to succeed,” he said it is also important to hear from whistleblowers. “What I don’t want this committee to do is to scare the you-know-what out of the American public,” he said. “In the end I want the public to be confident getting on an airplane. But I have to admit, this testimony is more than troubling…We have to be concerned. We have to get to the bottom of this.”