The Federal Aviation Administration has approved the inspection methodology for airlines to use on grounded Boeing 737 Max 9 aircraft.
The FAA issued the grounding order after a rearward door plug on an Alaska Max 9 aircraft blew out on Jan. 5, several minutes after takeoff from Portland. Alaska flight 1282 was able to descend from its altitude of about 16,000 feet and land in Portland without casualties.
The door plug is used by some Max 9 operators, including Alaska and United, in place of an exit door that would be required if the plane were configured with a larger number of seats.
The missing door plug was found Sunday in a residential yard. The National Transportation Safety Board has begun investigating the cause of the failure.
With an inspection plan issued, United, Alaska and other Max 9 operators can now begin working toward bringing grounded planes back into operation.
"The FAA's priority is always keeping Americans safe," the agency said in a Monday statement. "In that spirit, Boeing 737-9 aircraft will remain grounded until operators complete enhanced inspections, which include both left and right cabin door exit plugs, door components, and fasteners. Operators must also complete corrective action requirements based on findings from the inspections prior to bringing any aircraft back into service."
Airlines had been waiting to commence inspections while the FAA developed the formal methodology in consultation with Boeing. The grounding applies to approximately 171 planes globally, including 79 United planes and 65 Alaska planes. Another significantly impacted operator is Panama-based Copa, which flies 29 Max 9s. Inspections will take approximately four to eight hours each, the FAA estimates.
United didn't immediately offer a timeline for returning aircraft to service now that the inspection methodology is in place. Alaska also didn't put an inspection timeline forward in its most recent statement Monday. Both airlines said they had prepped their aircraft to be ready for inspection once the FAA approved the methodology.
On Monday, United had canceled 232 mainline flights by 1:30 Eastern time, according to FlightAware, amounting to 8% of its schedule. Alaska had canceled 147 flights, or 21% of its mainline schedule. United said it expected approximately 200 cancellations due to the Max 9 grounding.