Boeing CEO Dave Calhoun insisted the airplane maker had made significant changes to address a growing list of safety concerns during a testy two-hour hearing before a Senate subcommittee on Tuesday.

The hearing comes as the committee considers recommending the company for criminal prosecution in the wake of a Jan. 5 incident on an Alaska Airlines flight that lost a door plug midair.

“We have replaced every single leader across the executive leadership team between 2020 and where we are today,” Calhoun testified before the Senate Homeland Security and Governmental Affairs’s Permanent Subcommittee on Investigations. “I do believe in accountability. It’s hard to administer, but I believe in it and we have been working hard at that.”

Subcommittee chair Sen. Richard Blumenthal, D-Conn., included Calhoun’s departure at the end of the year as part of Boeing’s reckoning for a succession of safety incidents involving Boeing planes that have led to multiple federal investigations, including by the National Transportation Safety Board and Federal Aviation Administration.

Calhoun said a manufacturing defect led to the door plug blowing out on an Alaska Airlines flight in January, but he was not aware of any others. He said Boeing accepted responsibility for the software development error that led to a crash in Indonesia in 2018 and a crash in Ethopia in 2019 that together killed 346 people.

Before testifying, Calhoun apologized to the family members of the people who died during those crashes, saying, “I want you to know we are totally committed in their memory to work and focused on safety for as long as we’re employed.”

Calhoun took over as Boeing CEO in January 2020 but has come under fire this year amid reports of poor manufacturing practices that have led to loose bolts on some planes and lax oversight that led to the use of counterfeit titanium that affected the structural integrity of some aircraft.

“Accountability is very important for the past but also going forward for the future,” Blumenthal said during an acrimonious hearing that he said was certain to lead to the company’s prosecution by the Department of Justice. The senator said the company had submitted "gobbledygook" to the subcommittee's request for documentation.

Blumenthal repeatedly called out Boeing’s retaliation against whistleblowers who came forward with information about the company’s manufacturing practices at Boeing plants in South Carolina and Washington state.

Calhoun said the company, which employs 170,000, has “asked every one of our employees to consider themselves an aviation safety advocate. We’re committed to making sure every employee feels empowered to speak up if they see a problem.

He acknowledged the many reports about Boeing’s work culture, saying it “is far from perfect, but we are taking action and we are making progress.”

Sen. Josh Hawley, R-Mo., lambasted Calhoun for reports that the Boeing subcontractor who made the door plug on the Alaska Airlines plane was using Dawn dish soap, hotel room key cards and cheesecloth in their manufacturing operations.

After calling out Calhoun’s $33 million pay package, he accused Calhoun of “strip mining Boeing” for profits and encouraged the CEO to “recognize that Boeing has airplanes falling out of the sky.”

Boeing Chief Engineer Howard McKenzie testified, “The post-COVID moment in the aerospace industry has been unbelievably difficult to navigate. We have 10,000 suppliers. We put almost 2-1/2 million parts into a 787.”

He said the company has lost a lot of experienced employees, and the supply chain has also experienced “enormous turnover. So as we try to respond to unbelievable demand for airplanes, we have a supply constraint that is very real and it is not resolved today.”

Calhoun said the company has spent more than $1 billion to train workers. It has also increased its plane inspections.

In concluding the hearing, Blumenthal said he spoke for the entire committee when he said he wanted “Boeing to do well and succeed, but that requires a course correction. It requires a correction of that broken safety culture.”

Calhoun agreed, saying, “I am doing everything in my power.”