Wichita-based Spirit AeroSystems has provided another update to the National Transportation Safety Board investigation into the failed plug on an Alaska Airlines flight. The plug blew out during a flight over Oregon last Friday; the plane was a Boeing 737 Max 9 jet.
The plugs are installed in Max 9 fuselages by Spirit AeroSystems.
During a briefing late Monday, NTSB officials described how the plug on the flight rolled upward and flew off the jet. Four bolts and a dozen connecting points between the plug and the door frame are supposed to prevent that from happening.
On Wednesday, Spirit said a “team is now supporting the NTSB’s investigation directly. As a company, we remain focused on the quality of each aircraft structure that leaves our facilities.”
Boeing 737 Max 9 jetliners have been grounded by the Federal Aviation Administration until they could be inspected. Boeing didn’t provide inspection instructions until Monday.
On Tuesday, the FAA said those instructions were being revised “because of feedback,” and it extended the grounding of the planes.
“The safety of the flying public, not speed, will determine the timeline for returning the Boeing 737-9 Max to service,” the FAA said in a statement.
United canceled another 170 flights Tuesday because of the grounding; Alaska Airlines said it scrubbed 109 flights because it couldn’t fly the Max 9s.
It's not clear whether Spirit AeroSystems or Boeing technicians last worked on the door plug, which can be opened for maintenance.
Steven Wallace, former head of accident investigations for the FAA, said it was unlikely that Alaska crews worked on the plug because the plane was only delivered to the airline in October.
That means the investigation will likely focus on manufacturing, assembly and quality control, Wallace said.
Boeing stock fell 1% Tuesday, a day after plunging 8%; Spirit AeroSystems was nearly unchanged Tuesday after dropping 11% Monday.