WASHINGTON — More than a quarter of Air Mobility Command’s C-130 Hercules fleet are being temporarily removed from service after “atypical” cracking was found.

During scheduled depot maintenance, the U.S. Air Force discovered cracking of the lower center wing joint — also known as the “rainbow fitting” — which led Air Mobility Command head Gen. Maryanne Miller to order an inspection of a portion of the fleet, according to an AMC statement released Wednesday evening.

A total of 123 of 450 C-130H and C-130J aircraft will be temporarily grounded while inspections occur. “This temporary removal of service will not impact ongoing C-130 support to overseas contingency operations,” AMC said in its statement.

The decision to pause operations and conduct inspections was made after a single C-130 was found with the lower center wing joint cracks, said AMC spokesman Maj. Jonathan Simmons. But the risk posed by the issue — that the wing could become dislodged from the aircraft — was so serious that the Air Force decided to move forward with inspections for all planes that could potentially be impacted.

The 123 aircraft chosen to go through inspections have not been equipped with an “extended service life center wing box” and have flown more than 15,000 hours.

Maintainers will look for cracking, and, if discovered, will replace the rainbow fitting. That repair takes “approximately one to two months” to do and is “dependent on depot level availability and capacity,” Simmons noted in an email. Currently, AMC believes it has an adequate supply of rainbow fittings and is not concerned about a potential shortfall.

If no defects are found, the aircraft will return to service. So far, eight aircraft have gone through inspections and are now able to fly, Simmons said.

Each inspection is set to take eight hours, but the command does not know how long it will take to move all 123 aircraft through the inspection and repair process.

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“The Air Force takes the safety of its airmen and aircraft very seriously and is working diligently to identify and repair affected aircraft as soon as possible,” AMC said in its statement.