In the latest setback for Boeing (BA) - Get Boeing Company Report , the aircraft-maker has revealed that some parts for the 737NG and 737 MAX were possibly improperly manufactured.

The potential flaws were reported to the Federal Aviation Administration, which put out a notice on Sunday about the parts known as leading edge slat tracks.

"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," said the FAA. Some 32 NG jets and 33 MAX jets were identified to have the problem in the U.S. and 133 NG and 179 MAX aircraft worldwide were believed to be affected. 

"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," said the FAA.

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The FAA said it will put out an "Airworthiness Directive" to call for service by Boeing and to "identify and remove the discrepant parts" from service within 10 days.

Boeing has been hit hard since two 737 MAX jets were involved in fatal crashes in October and March over Indonesia and Ethiopia. Hundreds of passengers and crew were killed in the accidents.