On January 5, 2024 an Alaska Airlines Boeing 737 MAX 9 experienced a midflight blowout of a paneled-over section of fuselage commonly called a door plug. The airplane returned safely to Portland but the event triggered an NTSB investigation and immediate regulatory action.

Within 24 to 48 hours the FAA ordered U.S. operators to ground the subset of 737-9 MAX aircraft with that door plug configuration and issued an Emergency Airworthiness Directive requiring inspectors to examine left and right cabin door exit plugs, door components and fasteners before any return to service. The FAA made clear aircraft could not fly again until operators completed the enhanced inspections and any corrective actions specified by the directive. Approximately 171 airplanes worldwide were affected by the order.

Boeing provided a Multi-Operator Message with inspection instructions that was reviewed with the FAA. Operators were told the focused checks would take roughly four to eight hours per airplane, and that an FAA Alternate Method of Compliance would be needed to formalize how operators conduct the work and document findings. Airlines also awaited final maintenance and inspection documentation before large-scale returns to service.

What the preliminary inspections turned up

Early, preliminary checks by Alaska Airlines and United Airlines found instances of loose hardware and bolts that required additional tightening on some of the inspected door plugs. Those initial findings came from maintenance teams accessing the plug area as they prepared for formal inspections under the FAA directive. At the time regulators and Boeing were treating these as initial observations to be documented and analyzed by the NTSB and FAA.

Investigators noted key parts that secure the plug include upper and lower fasteners and multiple stop fittings around the plug perimeter. Officials were examining whether any bolts were missing, improperly installed, or had worked loose in service, and whether the issue was tied to manufacture, assembly, or maintenance processes. The NTSB took custody of recovered components for laboratory examination.

Operational and maintenance implications for operators

From a line operations perspective the grounding and required inspections are disruptive but necessary. Practical steps for operators include:

  • Prioritize aircraft by schedule impact and maintenance availability; expect four to eight man-hours per aircraft for the baseline inspection.
  • Use heavy maintenance checks when available to access plug structure thoroughly rather than relying solely on quick visual checks.
  • Document every finding with photos and torque readings and submit them to the FAA as required by the EAD.
  • If loose hardware is found, follow the corrective actions in the operator procedures and Boeing guidance; do not return an aircraft to service until the FAA approves the work.

What this means for Boeing and regulators

The incident exposed a hole in production, assembly or quality assurance controls somewhere in the supply chain or final assembly process. At this early stage the facts are limited to initial inspection findings and recovered parts. The NTSB remains the lead investigative agency for determining sequence and root cause, while the FAA will enforce corrective actions and oversight. The immediate industry priority should be a methodical inspection, careful documentation and a conservative approach to returning aircraft to service.

Bottom line for crews and passengers

For flight crews: treat the grounding and inspection program as a systems and maintenance issue, not an operational shortcut. If an aircraft has the affected plug configuration expect preflight or maintenance entries referencing the FAA EAD and operator compliance records. For passengers: the incident prompted real cancellations and schedule disruption, but the rapid regulatory response aimed to remove uncertainty and restore confidence through inspection and corrective work.

This is an unfolding investigation. The facts available as of January 10, 2024 point to loose or improperly secured hardware discovered in preliminary inspections and a robust FAA-directed inspection regime. The NTSB examination of recovered components and Boeing and supplier documentation will be the determinative sources for root cause findings, and operators must follow FAA-approved procedures before returning any affected 737-9 MAX to revenue service.