MIAMI – Boeing has informed the Federal Aviation Administration (FAA) about a manufacturing defect relevant to the leading edge slat tracks on a short amount of 737NG and 737 MAX aircraft.

It is understood that airlines affected will have 10 days to find the problems and remove the parts, with more airworthiness directives to be on the way from the 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 said.

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

Up to 148 parts produced by an unidentified “sub-tier supplier” have been marked as affected.

“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,” said the manufacturer.

On a global scale, this directive affects up to 133 Next Generation and 179 MAX aircraft. Boeing did concede that 21 737NGs will be the most likely to be affected, although it is waiting for 112 aircraft to be checked by the respective airlines.

First Boeing 737NG with Blended Winglets. (Credits: Boeing)

“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.”

The manufacturer has also mentioned that spare parts are on its way to those affected, with delivery times taking around two days on average.