Airlines have been told by regulators to inspect the door plugs on another class of Boeing jet following the mid-air blowout on an Alaska Airlines flight earlier this month.

The US Federal Aviation Administration late Sunday said companies operating Boeing 737-900ER jets should make sure equipment was properly secured.

The recommendation follows some operators reporting unspecified issues with bolts upon inspections.

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.”

A Boeing spokesman said: “We fully support the FAA and our customers in this action.”

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