The Federal Aviation Administration (FAA) on Sunday issued a statement alerting airlines and international aviation regulators that certain wing parts on more than 300 Boeing 737s may have been improperly manufactured and must be replaced within 10 days.

Both older model 737 NGs and new 737 MAXs are affected and there appears to be no connection with the recent fatal MAX crashes in Indonesia and Ethiopia.

The FAA said the parts in question are the slat track assemblies, used to guide the movable control surfaces on the leading edge of an airplane’s wings that deploy during takeoff and landing. Manufactured by a Boeing sub-tier supplier, a batch of up to 148 parts with specific lot numbers are affected, the FAA said.

Because the parts have been improperly manufactured, they may not meet regulatory requirements for strength and durability.

“The affected parts may be susceptible to premature failure or cracks,” the FAA said. “Although a complete failure of a leading edge slat track would not result in the loss of the aircraft, a risk remains that a failed part could lead to aircraft damage in flight.”

Boeing said it is issuing a Service Bulletin to 737 operators requiring inspections to identify and remove the faulty parts and the FAA will issue an Airworthiness Directive to mandate these actions be performed within 10 days.

Boeing said it is now staging replacement parts at customer bases to help minimize aircraft downtime while the work is completed. Once the new parts are in hand, the replacement work should take one to two days, Boeing said.

Following an investigation conducted by Boeing and the FAA, the jet manufacturer identified the serial numbers of both 737NG and 737 MAX airplanes on which these suspect parts may have been installed.


In a separate statement Sunday Boeing said it has identified 21 older model 737NGs and 20 new 737 MAXs most likely to have the parts in question. In addition, airlines are advised to check an additional 112 NGs and 159 MAXs.

Of the total of 312 airplanes potentially affected, 32 NGs and 33 MAXs are in the U.S.

All the 737 MAXs worldwide are currently grounded as Boeing seeks to certify a software fix for the flight control system implicated in two fatal crashes. The 179 with the suspected faulty parts will have to be inspected for this new, separate problem before the MAX fleet returns to service.

The 737 NGs with the suspected parts will have to be temporarily taken out of service for the inspections.

Boeing Commercial Airplanes chief Kevin McAllister said the company is “committed to supporting our customers in every way possible as they identify and replace these potentially nonconforming tracks.”