Boeing overwrote security camera footage of repair work on the door plug of an Alaska Airlines 737-9 plane that failed during a flight in January, federal inspectors said Wednesday.

Why it matters: The National Transportation Safety Board said in a letter to the Senate Committee on Commerce, Science, and Transportation that the missing footage is hampering its investigation into the accident.

• "To date, we still do not know who performed the work to open, reinstall, and close the door plug on the accident aircraft," the agency said.
• NTSB said it has been unable to interview the door crew manager at the Renton, Washington facility because he is out on medical leave.
• The agency in the letter stressed that it is not seeking to interview the workers that did the repairs for any punitive means but instead to learn about Boeing's quality assurance process.

Catch up quick: Alaska Airlines Flight 1282 safely returned to Portland International Airport just minutes after takeoff in January after part of the fuselage flew off at 16,000 feet for yet-unclear reasons.

What they're saying: "We will continue supporting this investigation in the transparent and proactive fashion we have supported all regulatory inquiries into this accident," Boeing said in an emailed statement.

• "We have worked hard to honor the rules about the release of investigative information in an environment of intense interest from our employees, customers, and other stakeholders, and we will continue our efforts to do so."
• When asked about the overwritten footage, Boeing responded: "Consistent with standard practice, video recordings are maintained on a rolling 30 day basis."
• The plan was at the Renton facility in September and delivered to Alaska Airlines in October, according to the NTSB's preliminary report.

State of play: This week a Federal Aviation Administration audit of Boeing's 737 Max jet production line found a plethora of issues with the production process.

• Boeing's woes are also hitting carriers like Southwest Airlines, which exclusively flies Boeing 737s.
• Southwest lowered its 2024 capacity growth projection as a result.

Go deeper: Boeing 737 Max production plagued by numerous problems, FAA audit finds