NTSB also said investigators still do not know who worked on door plug before it blew out mid-flight

The head of the National Transportation Safety Board (NTSB) said on Wednesday that investigators still do not know who worked on a Boeing 737 Max 9 door plug involved in the 5 January Alaska Airlines midair emergency and that video footage was overwritten.

The NTSB’s chair, Jennifer Homendy, said in a letter to senators that investigators sought security camera footage when the door plug was opened and closed in September but were informed the material was overwritten. “The absence of those records will complicate the NTSB’s investigation moving forward,” she said.

The NTSB said previously that four key bolts were missing from the door plug that blew out on the plane.