WASHINGTON — After seven months of investigation that generated 3,000 pages of records and 10 hours of testimony on Tuesday, it's still not clear to federal investigators how a dangerously flawed Boeing 737 MAX plane left the Renton factory.
Investigators from the National Transportation Safety Board circled around what happened in Boeing's Renton factory over two crucial days last September.
What's clear is that workers there reinstalled a panel incorrectly, leaving off four critical bolts that secure the panel in place. In January, that panel exploded off the plane on Alaska Airlines Flight 1282, shortly after it took off from Portland.
On Tuesday, representatives from Boeing, its key supplier Spirit AeroSystems and the International Association of Machinists, which represents the employees who likely worked on the panel, appeared before the NTSB. Board Chair Jennifer Homendy launched into the at times contentious hearing saying she was determined to stay put until all of the board's questions were answered.
At the close of the first day, it still wasn't clear exactly what went wrong.
Investigators did provide new details about the work surrounding those crucial moments, and shed light on long-standing issues at Boeing and Spirit that may have contributed to the nearly catastrophic incident. But the NTSB has yet to identify all of the workers involved in the crucial job, or determine why the bolts were missed.
"What we want to know is what happened in March, April, May, June, July, August, September, leading up to ... what happened in January," Homendy said in the Washington, D.C., hearing room.
"You can talk all about where you are today," Homendy told Elizabeth Lund, Boeing vice president of quality. But "what is very confusing for a lot of people who are watching, listening is what was going on then?"
The fuselage of the 737 MAX 9 that would later be at the center of the Alaska Airlines flight blowout rolled into Boeing's Renton facility on Sept. 1.
It arrived by train from Spirit's Wichita, Kan., factory and stayed at Boeing's Renton facility for two months, where Boeing workers installed the wings, tail and countless systems that make up a 737 MAX.
On the fuselage's first day in Renton, Boeing noticed an issue with five rivets near the mid-exit door plug — a panel that fits into a gap in the fuselage in which some airlines install an additional emergency exit — on the left side of the plane.
What caused a Boeing 737 MAX 9 door plug to detach during flight?
Four bolts on the sides of the door plug prevent it from moving upward. But in the accident on Alaska Airlines Flight 1282, the plug moved upward and fell out. Investigators believe the four bolts were removed during assembly at Boeing's Renton factory and not reinstalled.
Chris Brady, 737 Technical Guide (Fiona Martin / The Seattle Times)
Boeing filed a nonconformance order — the official paperwork to document a defect — to request that Spirit contractors based in Renton revisit the fuselage.
That triggered a dayslong battle between Boeing and Spirit about whether the fix had been completed. Spirit twice told Boeing it had made the correction. Boeing disputed that both times, and pushed the concern on to senior managers.
On Tuesday, Michael Riney, Spirit's on-site customer relations director for the Boeing Renton factory, told the NTSB the confusion came from a Spirit worker incorrectly signing off on the fix. That worker confused the plane with the faulty rivets with another aircraft they were working on the same day.
"He stated he had removed and replaced them, when in actuality he had not," Riney said.
Though that confusion ultimately could not have been the determining factor leading to the panel blowout, it illustrates a chaotic system of record-keeping at the Renton factory and points to tension between workers at the two different companies who are often scrambling to keep the plane moving down the assembly line.
In an interview with NTSB investigators, one Spirit worker described themself and their colleagues as the "cockroaches of the factory."
Riney told the board Tuesday that "our entire job is to get out of Boeing's way. We understand that we are inhibiting them."
After the panel blowout, Boeing began inspecting fuselages coming from Spirit before they ship to Renton. Boeing's Lund said Tuesday that that has led to an 80% decrease in defects. Boeing also recently secured a deal to buy Spirit, hoping to revitalize its troubled supplier.
But the fault for the blowout appears to lie with Boeing. Spirit workers would not be able to remove or reinstall a door plug, both Lund and Riney told NTSB investigators Tuesday.
In Renton last year, after Boeing escalated the issue with the rivets to senior-level management, it made the decision Sept. 15 to partially remove the door plug.
On Sept. 18, the panel was "fully opened" so it could lay flat, Lund told investigators on Tuesday. The problematic rivets were replaced and the door was closed the next day, Sept. 19.
But who replaced the door plug and who was responsible for ensuring it was reinstalled correctly is still a mystery.
Lund originally told investigators she believed a team called the "move crew," which prepares the plane to move outside, closed the door in order to finish their other tasks. She walked that back after NTSB investigators said that didn't match what they learned through the course of their investigation.
Board members said the move crew did need to adjust the door plug to complete its work. But the board said it is still unclear who closed the door on the 19th. Members from other teams could have been involved, Lund confirmed.
Boeing quality inspectors signed off on the rivet rework Sept. 19, Lund told investigators Tuesday. At that point, there was an opportunity to fill out paperwork to initiate the reinstallation of the door plug. But that never happened.
Through its investigation, the NTSB found 62 other cases since 2019 when Boeing had documented a removal for a similar door plug in production or on the flight line. When investigators asked Lund if there was anything different about those cases and this one, she said there was not.
"We have a gap," NTSB member Michael Graham remarked.
Lloyd Catlin, a Boeing employee based in Everett and member of the International Association of Machinists, testified Tuesday that the proper paperwork on a door plug removal, and the blankets that had been put in place around it, would have triggered another inspection.
That would have put "three sets of eyes on that door plug," and may have caught the missing bolts before the plane left the factory, Catlin said.
He went on to tell investigators that, even when using the proper channels to document work, Boeing had removed tens of thousands of inspections since 2016.
"There's some major issues the IAM has had over the last several years," he said.
Now, as Boeing works to repair its reputation following the door plug blowout, the company says it has added more inspections inside the planes it builds. Catlin disputed that.
When it comes to the door plug incident, the lack of documentation about reinstallation should have prevented other work from being done on the plane, Lund said. Instead, signing off on the rivet rework was the final step before that 737 MAX rolled out of the factory, one step closer to Alaska Airlines passengers.
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