The Federal Aviation Administration has issued a new warning to operators of Boeing 737-900ER aircraft instructing them to conduct visual inspections of mid-exit door plugs, structural components of the twin-engine narrow-body jets that are comparable to those that failed on a Boeing 737 MAX 9 jet earlier this month.
Mid-exit door plugs are panels installed to seal the passenger cabin in the place of an optional exit designed for the aircraft.
In the January 5 incident, an Alaska Airlines flight from Portland, Ore., to Ontario, Calif., experienced an in-flight emergency shortly after takeoff when a side panel in the cabin was blown open, depressurizing the aircraft. The jet returned to Portland and landed safely with all 171 passengers and six crew members.
The FAA has grounded more than 170 Boeing 737 MAX 9 jets pending inspections of the side door panels.
The 737-900ER aircraft is an extended range variant of the 737 900 from the previous generation of Boeing’s best-selling series, prior to the introduction of the 737 MAX, which started production in 2014. As the FAA noted in its Safety Announcement for Operators (SAFO), “Boeing 737-900ER mid-exit door plugs have an identical door plug design to the 737-9 MAX.”
FAA made it clear that there is no evidence of any problems or defects with the 737-900ER's mid-exit door plugs.
The agency noted that some operators have conducted additional inspections on 737-900ER mid-exit door plugs and noted findings with bolts during the maintenance inspections.
Among domestic operators, the 737-900ER is in service with Alaska Airlines, Delta Air Lines, and United Airlines. There are 380 of the aircraft in service worldwide, and collectively that variant has logged 11 million hours of flight operation, according to FAA.