Boeing is urging operators of 737 Max airplanes to look for a loose bolt in the rudder control system.
Boeing issued the recommendation under consultation with the FAA after an unnamed airline discovered a bolt with a missing nut while performing routine maintenance of a 737, the FAA said in a Thursday announcement. In addition, Boeing found an additional undelivered 737 Max with a nut that was not properly tightened.
"The issue identified on the particular airplane has been remedied," Boeing said in a statement. "Out of an abundance of caution, we are recommending operators inspect their 737 Max airplanes and inform us of any findings. We informed the FAA and our customers and will continue to keep them aware of the progress."
To date, there have been no in-service incidents caused by the bolt issue.
The FAA said it will remain in contact with Boeing and airlines while the inspections are underway. Each inspection will take an estimated two hours.
"The FAA will consider additional action based on any further discovery of loose or missing hardware," the agency said.
Quality-control issues have plagued the 737 Max. Most substantially, 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.