A manufacturing defect will require the replacement of leading edge slat tracks on a small subset of the global fleet of Boeing 737NG and Max aircraft.

Operators with affected aircraft have 10 days to identify and remove the discrepant parts, and an airworthiness directive will be issued, says the Federal Aviation Administration (FAA).

“Boeing has informed the FAA that certain 737NG and 737 Max leading-edge slat tracks may have been improperly manufactured and may not meet all applicable regulatory requirements for strength and durability,” it says.

“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 fight.”

The FAA adds that Boeing has identified up to 148 parts produced by an unidentified “sub-tier supplier” as being affected. Globally, the issue affects 133 NG and 179 Max aircraft.

In a statement, Boeing said that it has identified 21 737NGs mostly likely to have the parts in question. In the interests of being thorough has called on airlines to check an additional 112 NGs.

“A separate service bulletin will go to 737 Max operators to do inspections before the Max fleet returns to service,” adds the company. “Boeing identified 20 737 Max airplanes that are most likely to have the parts in question. Operators will be asked to check an additional 159 Max aircraft to ensure a thorough assessment.”

Boeing adds that it is sending replacement parts to customers to help minimise downtime. Replacement of the parts in question takes two days.

Cirium’s Fleets Analyzer indicates that there are 6,671 737NGs in service globally, and airlines have 385 737 Max jets in storage.

Source: Cirium Dashboard