Multiple whistleblowers alleged manufacturing and safety issues within Boeing aircraft models and dysfunctional safety culture throughout the company before a Senate panel on Wednesday.

Why it matters: The testimony comes as Congress and regulators seek to hold Boeing accountable after a mid-air blowout with one of its 737 MAX 9 jets during an Alaska Airlines flight earlier this year reignited safety concerns inside the company.

• The whistleblowers also criticized the Federal Aviation Administration (FAA) and other federal agencies for being over-reliant on companies like Boeing throughout their investigations and while carrying out oversight.

What they're saying: Sam Salehpour, a quality engineer at Boeing, built on his previous allegations that manufacturing defects in Boeing's 787 Dreamliner and 777 jets could cause the aircraft to break apart in flight.

• Salehpour on Wednesday told the Senate Permanent Subcommittee on Investigations he was sidelined, told to shut up and received threats after notifying company officials of the issues.
• He has specifically alleged that the company has failed to fill, or shim, tiny gaps between components that make up the aircraft's fuselages, which could eventually cause fatigue failure.
• "98.7% of the time, the gaps that they were supposed to be shimmed were not shimmed," he said.

The FAA confirmed last week that it is investigating Salehpour's claims.

Ed Pierson, executive director of the Foundation for Aviation Safety and a former Boeing engineer, said the FAA and the Department of Transportation were partly responsible for the alleged safety and manufacturing issues within Boeing and the 2018 and 2019 Boeing crashes that killed 346 people.

• "Government authorities ignored Boeing's manufacturing problems until the Alaska accident," Pierson said. "Passengers shouldn't have to rely on whistleblowers to provide the truth."
• "These agencies have become lazy, complacent and reactive," he said.

The other side: Boeing defended the safety of 787 and 777 in statements on Wednesday, saying it is "fully confident" in both planes. Previously, it said the allegations about the structural integrity of 787 aircraft were "inaccurate."

• The company also said it is on "a continuous improvement journey on ensuring that our teammates opinions and questions get answered" and encourages employees to speak up.

The big picture: Preliminary findings from an investigation into the 737 MAX 9 blowout earlier this year suggested that missing bolts were the likely cause.

• An FAA audit against Boeing earlier this year unveiled a series of issues with the production process, non-compliance issues in the company's manufacturing process control, parts handling and storage, and product control.

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