The US Air Force (USAF) has reportedly grounded 13 of its F-35 Lightning II joint strike fighter aircraft, following the discovery of peeling and crumbling insulation in avionics cooling lines inside the fuel tanks.
The decision comes within two months of declaring the initial squadron of the F-35A as combat ready.
USAF spokeswoman Ann Stefanek was quoted by Reuters as saying: "The issue was discovered during depot modification of an F-35A and affects a total of 57 aircraft.”
Of the 15 aircraft grounded, 13 belong to the US and the remaining two to the Royal Norwegian Air Force.
Ten of them were declared combat ready, one was being used in testing, and the remaining four were being used for training, reported CNN.
Production of another 42 aircraft is currently underway.
CNN quoted representatives from the USAF and Lockheed Martin's F-35 programme as saying that the defective cooling lines were not found in all the aircraft as the faulty part was used by only one sub-contractor that did not work on all the planes.
A team comprising engineers of the F-35 Joint Program Office and Lockheed Martin and Air Force maintenance teams at Hill Air Force Base in Utah are working on fixing the problem.
Stefanek further added: "The Air Force is also working with units to mitigate the impact on operations, training, and readiness.”
Image: A USAF F-35A Lightning II. Photo: courtesy of US Air Force photo by Master Sgt. Donald R. Allen.