The Federal Aviation Administration is now calling for airlines to "visually inspect mid-exit door plugs" of Boeing 737-900ER aircraft as it continues its review of grounded Boeing 737-9 MAX planes in the wake of a Jan. 5 Alaska Airlines incident.
The FAA said in a statement that "as an added layer of safety," it recommends operators of Boeing 737-900ER aircraft take a closer look at the planes to "ensure the door is properly secured.
"The Boeing 737-900ER is not part of the newer MAX fleet but has the same door plug design," it added.
The door plug on a 737-9 MAX plane detached just minutes after Alaska Airlines Flight 1282 took off from Portland, Oregon on Jan. 5 and reached 16,000 feet. The loss of the plug caused the cabin to depressurize, and a gaping hole sucked out cell phones and ripped a child's shirt off his body.
The FAA announced last Wednesday that "All 737-9 MAX aircraft with door plugs will remain grounded pending the FAA’s review and final approval of an inspection and maintenance process that satisfies all FAA safety requirements."
"Once the FAA approves an inspection and maintenance process, it will be required on every grounded 737-9 MAX prior to future operation," it said at the time. "The safety of the flying public, not speed, will determine the timeline for returning these aircraft to service."
At least 40 inspections of Boeing 737-9 MAX aircraft are now complete.
The FAA also said earlier this month that the Alaska Airlines incident "should have never happened and it cannot happen again.
"FAA formally notified Boeing that it is conducting an investigation to determine if Boeing failed to ensure completed products conformed to its approved design and were in a condition for safe operation in compliance with FAA regulations," it also said.
Fox Business’ Breck Dumas contributed to this report.