Pentagon testers for the F-35C reported a crack on the wing spar of a test aircraft, prompting contractor engineers to formulate a solution.

The cracks were discovered on a heavily tested plane in a main structural element on the C-variant of the Lockheed Martin-made F-35 Lightning II, which is for use on U.S. Navy aircraft carriers. The damage is not expected to affect the current flight operations for any of the variants currently in service for the U.S. military, however the cost of retrofits are not yet known.

"Initial estimates indicate a modification of approximately a half a pound to the aircraft will fix it," Pentagon spokesman Joe DellaVedova told IHS Janes. "Modifications to planes flying today will be incorporated to ensure full life operation."

Defense News reports the F-35C test aircraft sustained the damage during durability ground testing, which involves the application of cyclic loads to the airframe to identify potential problems.

DellaVedova went on to detail the jet in question's rigorous use, saying the plane has accumulated over 13,700 test hours, comparable to about 20 years of a plane's operational military service. All F-35s flying today have about 250 or fewer flight hours logged.

The adjustments made to the cracked test plane will be applied to the rest of the fleet.