The U.S. Federal Aviation Administration late Sunday recommended airlines operating Boeing 737-900ER jets inspect door plugs to ensure they are properly secured after some operators reported unspecified issues with bolts upon inspections.The recommendation follows the FAA’s grounding of 171 Boeing 737 MAX 9 planes after the mid-air cabin blowout of a door plug on an eight-week-old Alaska Airlines MAX 9 jet on Jan. 5.The 737-900ER is not part of the newer MAX fleet but has the same door plug design that allows for the addition of an extra emergency exit door when carriers opt to install more seats.The FAA issued a „Safety Alert for Operators“ disclosing some airlines have conducted additional inspections on the 737-900ER mid-exit door plugs „and have noted findings with bolts during the maintenance inspections.“
It recommended air carriers perform key portions of a fuselage plug assembly maintenance procedure related to the four bolts used to secure the door plug to the airframe „as soon as possible.“
A Boeing spokesperson said in an email that „we fully support the FAA and our customers in this action.“Alaska Airlines and United Airlines, the only two U.S. carriers that use MAX 9, said this month they had found loose parts on multiple grounded MAX 9 aircraft during preliminary checks. They have had to cancel thousands of flights this month because of the grounding.United said on Sunday it was extending the cancellation of its MAX 9 flights through Jan 26.
Both carriers said they had begun inspections of the door plugs on their 737-900ER fleets.
United, which has 136 737-900ER aircraft, expects them „to be completed in the next few days without disruption to our customers.“
Alaska said its inspections began several days ago and it has „had no findings to date and expect to complete the remainder of our -900ER fleet without disruption to our operations.“
Delta Air Lines, which operates the 900ER, said it had „elected to take proactive measures to inspect our 737-900ER fleet“ and does not anticipate any operational impacts.
The Boeing 737-900ER has over 11 million hours of operation and 3.9 million flight cycles. The FAA said the door plug „has not been an issue with this model“ and by contrast, the MAX 9 that experienced the door-plug issue was a new plane with a low number of flights.
On Wednesday, the FAA said inspections of an initial group of 40 Boeing 737 MAX 9 jets had been completed, a key hurdle to eventually ungrounding the model. The FAA is continuing to review data from those inspections.
It said on Sunday that the MAX 9 will „remain grounded until the FAA is satisfied they are safe to return to service.“