June 2 (UPI) -- The Federal Aviation Administration said Sunday it has been informed by airplane manufacturer Boeing that "improperly manufactured" parts may have been installed in its 737 airplanes.
Working with Boeing, the FAA said in a statement it identified 148 slat tracks manufactured by a sole sub-tier supplier to be affected.
Boeing said it identified 21 of its 737 Next Generation planes and 20 of its 737 Max aircraft to most likely contain the affected parts while having instructed for an additional 112 NGs and 159 Maxs to undergo a "thorough assessment."
The FAA, however, said 32 NGs and 33 Maxs in the United States and 133 NGs and 179 Maxs worldwide may contain the faulty parts.
"Boeing is now staging replacement parts at customer bases to help minimize aircraft downtime while the work is completed," Boeing said Sunday in a statement. "Once the new parts are in hand, the replacement work should take one to two days."
Boeing said it had not been informed of any issues related to the slat track, which "are used to guide slats located on the leading edge of an airplane's wings."
The FAA said the affected parts may be susceptible to failure or cracks but that a complete failure of the part "would not result in the loss of the aircraft" though it could lead to aircraft sustaining damage in flight.
The FAA will issue an Airworthiness Directive, which gives operators of affected aircraft 10 days to remove the parts, it said, adding that international civil aviation authorities have also been notified.
Boeing's 737 Max 8 and Max 9 aircraft have been grounded since March following two fatal crashes that killed a combined 346 people.
On Sunday, Kevin McAllister, president and CEO of Boeing's Commercial Airplanes, said in a statement that "we are committed to supporting our customers in every way possible as they identify and replace these potentially non-conforming tracks."