Video of work on Boeing door plug has been lost, U.S. investigators say

The head of the U.S.National Transportation Safety Board (NTSB)saidon Wednesdayinvestigators still do not know who worked on aBoeing737 MAX 9doorplug involved in an Alaska Airlines mid-air emergency and that video footage was overwritten.

NTSB Chair Jennifer Homendy said in a letter tosenators that investigatorssought security camera footagewhen thedoorplug was opened and closedin September but were informed the material was overwritten.

"The absence of those records will complicate the NTSB's investigation moving forward," Homendy said.

The NTSB said previouslythatfour key bolts were missing from thedoorplug that blew out on the plane.

Alaska Airlines Flight 1282 had 171 passengers and six crew on board and was flying at an altitude of more than 4,800 metres when a door plug a panel in place of an optional exit door located near the rear of the aircraft ripped off about 20 minutes into the Jan. 5 evening flight from Portland, Ore., to Ontario, Calif.

Fortunately, the two seats next to the panel were vacant and there were no serious injuries, though several passengers did require medical attention after the pilots made an emergency landing at Portland International Airport.

Last week, Homendy said she spoke toBoeingCEO David Calhoun "and asked for the names of the people who performed the work. He stated he was unable to provide that information and maintained thatBoeinghas no records of the work being performed."

Boeingdid not immediately comment.

The Justice Department has opened a criminal investigation into the mid-air emergency.

On Friday,Boeingsaid it believes required documents detailing the removal of thedoorplug during production were never created.

Boeingsaid its working hypothesis was "the documents required by our processes were not created when thedoorplug was opened."

Homendy last week criticized what she calledBoeing's lack of co-operation and failure to disclose some documents, including on thedoorplug opening and closing, as well as the names of 25 workers on thedoorcrew at the 737 factory in Renton, Wash. After Homendy's comments,Boeingprovided the 25 names.

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In the aftermath of the incident, the Federal Aviation Administration (FAA) grounded the MAX 9 for several weeks in January, barredBoeingfrom increasing the MAX production rate and orderedBoeingto develop a comprehensive plan to address "systemic quality-control issues" within 90 days.

Separately, the NTSB wroteBoeingon Wednesday reminding them they face restrictions on information they can release publicly as a party to the investigation.

"Releasing investigative information without context is misleading to Congress and the public and undermines both the investigation and the integrity of the NTSB," Homendy wrote.