A source familiar with Boeing's manufacturing process stated that the company doesn't usually modify the type of panel implicated in the recent 737 MAX 9 incident unless a problem is detected during factory tests. It was reported that Spirit AeroSystems, a supplier for Boeing, delivers partially assembled fuselages to Boeing with a special panel, which serves as a substitute for an optional emergency exit, installed but not finalized.
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Typically, Boeing employees remove this panel to install cabin equipment, then reattach the panel and complete the installation. However, the source clarified that Boeing only removes or adjusts the panel if there are indications of incorrect installation, as per their standard factory procedures. Before delivering the aircraft to the airline, Boeing conducts certain checks and pressurization tests. The interior of the plane is loaded at a different location. These sources were discussing standard production procedures, not specifically the incident involving an Alaska Airlines jet that had to make an emergency landing due to a panel tearing off mid-flight, leaving a large hole in the fuselage. Understanding these industrial processes related to Boeing's largest single-aisle plane will aid investigators in determining if the accident was caused by design or manufacturing issues.
Both Boeing and Spirit AeroSystems declined to comment. The production practices, which couldn't be independently verified, are currently under investigation by the Federal Aviation Administration (FAA). The National Transportation Safety Board is conducting a separate investigation into the accident's causes. The sources chose to remain anonymous due to ongoing investigations. The FAA, which took over the responsibility of approving individual MAX planes after a previous safety crisis, has initiated a formal investigation into the MAX 9. FAA chief Mike Whitaker views the MAX 9 issues as a manufacturing problem, not a design flaw.
The aerospace industry is currently facing challenges due to supply and labor shortages, forcing many manufacturers to find alternative solutions to maintain production, which complicates the monitoring of exact production flows. The Air Current reported that Boeing typically doesn't remove the plug for the optional emergency exit unless there's an installation or "rigging" issue and that Boeing does conduct quality checks. The door plug on an Alaska Airlines jet detached at 16,000 feet during ascent from Portland, Oregon, on January 5, leading the FAA to ground over 170 similar aircraft. The source familiar with Boeing's manufacturing process explained that the plug is held in place inside the aircraft fuselage by four bolts, which prevent the plug from moving up and down. It's unclear when these bolts are secured during the production process or what checks Boeing is responsible for. Industry sources briefed on the matter reported conflicting accounts of who does what, with at least one source questioning the completeness of the panel installation when the fuselages depart from Spirit. Once the aircraft is in service, airlines usually remove the plug every couple of years for maintenance. The source added that cabins are loaded through larger doors. Quality controls are being scrutinized after airlines reported loose bolts in other aircraft following the accident.
