The National Transportation Safety Board’s investigation into a terrifying January 5 mid-air blow-out of a door plug aboard a Boeing 737 MAX 9 has hit yet another snag. 

It was initially revealed in February that the four bolts that would have kept the plane’s door plug in place were missing from the aircraft prior to takeoff. But since then, the NTSB has highlighted its struggles getting the names of Boeing employees who may have worked on the plane when it went in for rivet repairs in September 2023 at the company’s Renton, Washington facility. 

In a March 13 letter from NTSB chair Jennifer Homendy to the U.S. Senate transportation committee, Homendy lays out the progress of the investigation so far, detailing how Boeing has been unable to produce any records of the September rivet repair work.  

According to Homendy, Boeing CEO Dave Calhoun admitted that the company doesn’t have those specific records at all, and was only able to provide the names of workers who reported to the door crew manager in September. 

Perhaps even more concerning, the NTSB also found that Boeing overwrote surveillance footage of the Renton repair facility where the repairs were done. No explanation was given for why the footage was not kept. 

That has the NTSB worried that the “focus on the names of individual front-line workers” could discourage those employees from giving the NTSB information that would help move the investigation forward. 

“To that end, I have instructed NTSB to utilize our authority to protect the identities of the door crew and other front-line employees who come forward with information relevant to the investigation,” Homendy promised.  

In the meantime, without the names of the people who worked on the aircraft or the surveillance footage of the facility from September, Homendy warns that “the absence of those records will complicate the NTSB’s investigation moving forward.”