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This story has been updated to reflect the latest reporting.
The Federal Aviation Administration announced on Jan. 6 that it will order certain Boeing 737 Max 9 airplanes operated by U.S. airlines or in U.S. territory to undergo inspections before returning to flight.
The action was prompted by the incident on Jan. 5 in which a new Alaska Airlines Max 9 unexpectedly lost its plugged rear-aft door on climb-out from Portland, Oregon, necessitating an immediate return to the airport. No one on board was injured in the incident.
Related: Alaska launches temporary grounding of 737 Max 9 fleet
In a statement, the FAA said it would issue an emergency airworthiness directive (EAD) that will require operators to inspect Max 9 aircraft that do not meet the inspection cycles specified in the EAD. The Air Current has learned that the required inspection is a normal part of the aircraft’s C checks, which means that some recently inspected Max 9 airplanes are already in compliance.
That is why Alaska Airlines was able to resume operating some Max 9s early on Jan. 6 after announcing that it would ground its fleet pending maintenance and safety inspections. An Alaska memo that was sent to flight crew personnel and reviewed by TAC stated: “This inspection was written specifically for this task and provided to us by Boeing. Of the 66 aircraft on property, 18 had already been inspected in a recent heavy maintenance check and therefore those 18 we cleared to continue flying.”
The memo added that “the required inspections of the remaining tails began immediately, and good progress has been made.” The airline expected to have all inspections completed and all Max 9s cleared to fly by sometime on Monday, Jan. 8.
Alaska and Boeing did not immediately respond to a request for comment on the heavy check procedure.
Heavy checks on 737s occur every 4,000 to 6,000 hours or roughly every two to three years. Alaska received its first Max in January 2021 shortly following the resumption of service for the aircraft in the U.S. after the more than 600 day grounding prompted by fatal Max crashes in 2018 and 2019.
Meanwhile, United Airlines said it “has temporarily suspended service on select Boeing 737 Max 9 aircraft to conduct an inspection required by the FAA. We are working directly with impacted customers to find them alternative travel options.”
United has 79 Boeing 737 Max 9 aircraft, including about 33 that have already received the necessary inspection that is required by the FAA. Removing certain Max 9 aircraft from service is expected to cause about 60 cancellations today.
The FAA said that the required inspections will take around four to eight hours per aircraft and will affect approximately 171 airplanes worldwide. Boeing has delivered a total of 218 737-9s.
While no root cause for the failure has been identified, the regulatory action ordered by the FAA implies that the agency is confident that any issue that presented itself on Alaska’s Max 9 can be mitigated through a known heavy check procedure.
“Safety will continue to drive our decision-making as we assist the NTSB’s investigation into Alaska Airlines Flight 1282,” FAA Administrator Mike Whitaker said in the agency’s statement.
The NTSB announced that it has launched a Go Team to Portland, Oregon to investigate the event. NTSB Chair Jennifer Homendy will be on scene as the agency’s spokesperson.
