The U.S. Federal Aviation Administration has 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.
This is an older Boeing (BA.N) model that used a system of plugs similar to those on the Boeing 737 MAX 9, most of which have been grounded following the Jan. 5 blowout of a door plug on an Alaska Airlines MAX 9 (ALK.N).
Not all the Boeing 737-900ER have the door plugs and all 737-900ERs have had maintenance checks at least once since they were delivered, so checking them has not had the same urgency.
The door plugs - which replace an unused emergency exit - are most likely to exist on planes with fewer than 189 seats, above which airlines must use the same space for an active door in order to provide the right number of evacuation paths.
Here is a breakdown of Boeing 737-900ER jets currently in service, with the average number of seats per plane, extracted from data provided by aviation analytics firm Cirium.
There are 490 of the planes in service, of which 79 have the higher-density configuration with 189 or more seats, requiring a door rather than a plug. Some of the jets have been traded since they were delivered, meaning they originally had more seats.
