Four bolts were missing from the Boeing Alaska Airlines aircraft door which blew out mid-flight, a preliminary investigation by the US National Transportation Safety Board (NTSB) has found.
The door panel, known as a plug, had been removed to fix rivets damaged in production. Those bolts were removed at a Boeing factory in Washington and appear not to have been replaced, according to the report.
Dave Calhoun, CEO of Boeing, said in a statement: “Whatever final conclusions are reached, Boeing is accountable for what happened.
“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.”
The NTSB report released on Tuesday focused on how the panel could have detached from the plane.
Records from September showed five rivets were damaged on the frame of the door plug. All 12 stop fittings disengaged during the flight, the NTSB stated in January.
Yesterday’s report said “the investigation continues to determine what manufacturing documents were used to authorise the opening and closing of the plug during the rivet rework”.
Representative Rick Larsen, who is on the committee overseeing the Federal Aviation Administration (FAA), said the “failure to re-install bolts on a safety-critical component of this 737 MAX 9 aircraft is a serious error that signals larger quality control lapses that must be corrected”.
The FAA grounded 171 of the Boeing 737 MAX 9 planes after the incident, most operated by US carriers United Airlines and Alaska Airlines.
In the days after the blowout, the two airlines found loose parts on multiple grounded MAX 9 aircraft.
Those planes were cleared to return to service in late January and nearly all are flying again, according to Reuters.
The incident has since raised serious concerns amongst airlines over slipping safety standards at Boeing.
On Monday, Emirates boss Sir Tim Clark said he had seen a “progressive decline” in standards at Boeing and that the company was in the “last chance saloon” as he prepared to send his own engineers to oversee the plane maker’s production line.
He told the Financial Times a drop in standards had likely been caused due to long-running management and governance mis-steps, which included prioritising financial performance over engineering excellence.
Image: An Alaska Airlines Boeing 737 MAX 9 comes into land (Credit: @IanDewarPhotography/Adobe Stock)