The US Air Force grounded over 100 workhorse C-130 transport planes after discovering unusual wing cracks

The US Air Force has decided to pull 123 C-130 transport aircraft out of service after “atypical cracks” were discovered on the wings, Air Mobility Command announced.

The C-130, a type of plane of which there are many variants for different tasks, is an important workhorse aircraft for the Air Force, which operates a total of 450 C-130s.

The decision to ground nearly one-third of the service's C-130 fleet comes as the Air Force struggles to maintain high mission capable rates for its aircraft.

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The US Air Force has decided to pull nearly a third of its C-130 transport aircraft out of service after discovering “atypical cracks” on the wings, Air Mobility Command (AMC) revealed.

After consulting with maintenance and engineering teams, AMC Commander Gen. Maryanne Miller decided that it was necessary to temporarily remove 123 of the Air Force's 450 available C-130s from service after cracks were discovered on the lower center wing joint, or “rainbow fitting,” during depot maintenance.

“General Miller directed an immediate time compliance technical order inspection to identify and correct any cracking to ensure airworthiness of these C-130 aircraft,” Air Mobility Command said in a statement Thursday. “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 says that that the removal of more than one hundred C-130s, a workhorse for the Air Force, will not affect overseas operations.

Read more: Step inside the C-130, the super-versatile workhorse that flies Navy SEAL missions, delivers supplies to Antarctica and fights wildfires

Each C-130 transport aircraft requires roughly eight hours to fully inspect. If a plane is found to have a problem, it will be repaired; otherwise, it will be returned to service. Eight aircraft have been inspected and returned to service, Task & Purpose reported, citing an AMC spokesman.

The latest move, as Air Force Magazine notes, follows a decision earlier this year to ground around 60 C-130s due to propeller issues. The Air Force began looking closely at these issues after a damaged blade caused a C-130 tanker crash that killed 16 US service members; a maintenance depot failed to properly fix the blade.

The Air Force has been struggling as mission capable rates for aircraft have declined in recent years, dropping from 77.9 percent in 2012 to 69.97 percent last year. It recently came to light that only 7 of the Air Force's 61 B-1 bombers are ready to fly.

Read more: The Air Force has 61 B-1B bombers, but just 7 of them are ready to fight