Boeing has informed the FAA that certain 737NG and 737MAX leading edge slat tracks may have been improperly manufactured and may not meet all applicable regulatory requirements for strength and durability.

Following an investigation conducted by Boeing and the FAA Certificate Management Office (CMO), we have determined that up to 148 parts manufactured by a Boeing sub-tier supplier are affected. Boeing has identified groups of both 737NG and 737MAX airplane serial numbers on which these suspect parts may have been installed. 32 NG and 33 MAX are affected in the U.S. Affected worldwide fleet are 133 NG and 179 MAX aircraft.

The affected parts may be susceptible to premature failure or cracks resulting from the improper manufacturing process. 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.

The FAA will issue an Airworthiness Directive to mandate Boeing’s service actions to identify and remove the discrepant parts from service. Operators of affected aircraft are required to perform this action within 10 days. The FAA today also alerted international civil aviation authorities of this condition and required actions.

FAA release