The Federal Aviation Administration (FAA) is “closely monitoring” targeted inspections of Boeing 737 MAX airplanes to look for a possible loose bolt in their rudder control systems.

Under consultation with the FAA, Boeing has issued a multi-operator message (MOM), urging operators of newer single-aisle airplanes to inspect specific tie rods that control rudder movement for possible loose hardware.

The FAA will remain in contact with Boeing and the airlines while the inspections are underway. The agency is asking the airlines to work through their approved safety management systems to identify whether any loose hardware has been detected previously and to provide the agency with details on how quickly these two-hour inspections can be completed.

The FAA will consider additional action based on any further discovery of loose or missing hardware. Boeing recommended the inspections after an international operator discovered a bolt with a missing nut while performing routine maintenance on a mechanism in the rudder-control linkage. The company discovered an additional undelivered aircraft with a nut that was not properly tightened.

Quality-control issues have plagued the 737 MAX. The aircraft was grounded globally for 20 months beginning in the spring of 2019 following the second of two crashes that killed a combined 346 people. The crashes were caused by a faulty sensor, which transmitted erroneous information to the planes’ automated flight-control system, causing the aircraft to nosedive.

Boeing also delayed MAX deliveries last April after it discovered that parts supplier Spirit AeroSystems used a nonstandard manufacturing process on fittings near the rear of dozens of 737 Max planes. Deliveries resumed in May.

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