Air Force, Norway suspend F-35 flight operations

The U.S. Air Force and Norway have both ordered a temporary pause in flight operations for 15 Joint Strike Fighter aircraft after discovering "peeling and crumbling" insulation inside of avionics cooling lines in the jets' fuel tanks.

The defect was discovered during an F-35A conventional-take-off-and-landing variant depot modification, according to a Sept. 16 Air Force statement.

In the Sept. 16 statement, Air Force spokeswoman Ann Stefanek said the problem was discovered while an aircraft was undergoing depot modifications and affects 57 aircraft -- 15 in the field and 42 in production.

"Engineers with the F-35 joint program office and Lockheed Martin and Hill Air Force Base maintenance airmen have conducted inspections of eight aircraft and are currently developing procedures to resolve or mitigate the issue prior to release of affected production aircraft to the field and the return of affected operational aircraft to flight operations," the statement reads, noting that the service is working to lessen the impact on operations, training and readiness. "Subject matter experts are considering courses of action to mitigate these delays."

The statement also contends that because the F-35 is still in development, "challenges are to be expected."

"The F-35 program has a proven of solving issues as they arise and we're confident we'll continue to do so," it states.

In a separate statement, Norwegian Maj. Gen. Morten Klever, F-35 program office director said: "We have been very pleased with our aircraft so far, both in terms of performance and technical capabilities. This is not a design flaw, but is instead caused by a supplier using improper materials and improper sealing techniques for these specific parts."

Norway has received four F-35A conventional-takeoff-and-landing aircraft that are operating at Luke Air Force Base in Arizona.

"The issue has been traced back to cooling line manufactured by one particular provider that have only been installed in the wing fuel tanks of 15 aircraft -- 13 U.S. and two Norwegian," according to the statement. "Additionally, 42 aircraft currently on the production line have received parts from the same provider, including three Norwegian aircraft scheduled for delivery early next year."