The US Federal Aviation Administration (FAA) has issued a Safety Alert for Operators (SAFO) recommending checks on B737-900ER emergency door plugs given their similarities to plugs installed on the B737-9.

"The Boeing 737-900ER mid-exit door plugs have an identical door plug design to the B737-9 MAX. As part of their Safety Management Systems, some operators have conducted additional inspections on the B737-900ER mid-exit door plugs and have noted findings with bolts during the maintenance inspections... Operators are encouraged to conduct a visual inspection to ensure the door plug is restrained from any movements," the regulator said.

The checks are not mandatory, and the type has not been grounded.

The SAFO is a consequence of the January 5, 2024, incident, when Alaska Airlines' B737-9 N704AL (msn 67501) suffered an in-flight door plug blowout. The incident prompted the FAA and other regulators globally to issue Emergency Airworthiness Directives and ground the type pending investigation.

The emergency door plugs are installed on B737-900ERs and B737-9s which are configured for a smaller than maximum number of passengers and do not need the additional, fifth pair of doors for emergencies. The doors are permanently plugged into the fuselage and are inactive, and usually are not visible from the inside of the cabin (as opposed to inactive but non plugged doors).

The ch-aviation fleets module shows that there are 414 B737-900ERs configured for 189 or fewer passengers - a number that does not necessitate the active fifth pair of emergency doors. This pool includes the following operators:

Not all of the aircraft seating fewer than 189 passengers necessarily have their fifth emergency door pair plugged in. The FAA SAFO only pertains to carriers operating those aircraft in and to the United States.