Following a supply chain glitch that delivered the wrong material for the tubing insulation on 15 Lockheed Martin F-35As, the US Air Force has identified a solution and will fix the issue with the original supplier, according to the F-35’s executive officer of the joint programme office.

Last week, the USAF revealed that a supplier used the wrong coating for the insulation which deteriorated when it met fuel. The crumbling insulation clogged the vent between the wing tank and fuselage tank, but would not affect the engine’s performance, Lt Gen Chris Bogdan said at annual Air Force Association conference Tuesday.

Lockheed will pay for engineering and modifications for all affected aircraft, including 15 USAF and Norwegian fighters and 42 on the production line. Although the issue affected some aircraft in lot 9, the tubing problem will not affect lot 9 contract negotiations and the air force expects an agreement by the end of the year, Bogdan says. The USAF intends on correcting the tubing issue and continuing with the same supplier, if they can deliver a quality product, he adds.

“Once we found the insulation issue we quickly corrected it with the company,” Bogdan says. “We sent our guys and Lockheed quality guys to make sure the PAO lines they’re now delivering are fully qualified.”

The supplier, which both Lockheed and the USAF have not identified, was a second source brought on last year as an insurance measure for the production ramp up, Bogdan says. The insulation issue will not affect the B and C variant of the F-35 because the company had decided to start as a smaller supplier confined to the F-35A, he says.

The USAF has prioritized fixing the fielded aircraft, but the service will begin modifications in the next month on two F-35As for Israel that are slated for delivery in December. The maintenance issue affected 42 production line aircraft, which the USAF, Israel, Norway, Japan and Italy have not yet accepted.

The air force is conducting a risk assessment on all 15 of the temporarily grounded F-35As and should complete the study within the week, Bogdan says.

“Based on the damage we’ve seen from the inspections, we could get back in the air while they’re waiting to get fixed,” Bogdan says. “One of the things helping us is the tubes inside the fuel tank are at the leading edge of the wing. To get little pieces of the insulation from the front of the wing, all the way back to the back of the wing is really a difficult process.”