Missing bolts were attributed as the cause of a part blowing off midflight on an Alaska Airlines flight on Jan. 5, according to a preliminary report filed by the National Transportation Safety Board.
According to CBS News, “The door plug, which covers an unused exit door, is typically secured with four bolts to prevent it from moving vertically.”
The report said it was intact after leaving the manufacturer Aug. 20, Boeing subcontractor Spirit AeroSystems, but on Sept. 19, it shows the door missing the bolts after it was removed for repair, per The New York Times.
With the report, it is “likely to increase the pressure on Boeing, one of the world’s largest airplane makers,” The Washington Post reported.
“Whatever final conclusions are reached, Boeing is accountable for what happened,” Boeing chief executive Dave Calhoun said, per the Post. “An event like this must not happen on an airplane that leaves our factory. We simply must do better for our customers and their passengers.”
In a statement, Boeing said it adapted its processes and “developed new protocols” in order to better document how the door will be removed and reattached, per the Times.
What we know about the Alaska Airlines flight
The Alaska Airlines flight carrying 171 passengers and six crew members was grounded earlier this month after a fuselage door plug blew off midflight, with a force strong enough that it blew open the cockpit door, Reuters reported.
A Portland teacher discovered the part in his backyard shortly after federal investigators asked for the public’s help in finding the missing part, according to CNN.
“Our structures team will want to look at everything on the door — all of the components on the door to see, to look at, witness marks, to look at any paint transfer, what shape the door was in when found. That can tell them a lot about what occurred,” National Transportation Safety Board Chair Jennifer Homendy said, per Reuters.
One of the theories about what happened to the part is “that the bolts that were supposed to keep a fuselage panel in place were never installed before the panel blew off,” the Times reported.
What happened during the flight when the part blew off?
No passengers were seated in the section where a “refrigerator-sized hole” was blown out of the plane. There was also a headrest torn from a seat in the section.
“It’s fortunate that nobody died and there were not more serious injuries,” Homendy told CNN.
What happens now?
Following the incident, the Federal Aviation Administration grounded all Boeing 737 Max 9s until it’s “satisfied that they are safe,” an FAA spokesperson said, per CBS News.
According to The New York Times, “a pressurization warning light had gone off during three recent flights,” so the airliner hadn’t been used in long flights over water. The aircraft hadn’t been worked on before the flight, and workers had “reset the system and the plane was put back into service.”
The safety board is still investigating the incident.