NATIONAL HARBOR, Md. — The Defense Department is considering a plan that would keep about one hundred F-35s in an earlier software configuration not optimized for combat.

According to a FlightGlobal report, Lockheed Martin delivered about 108 aircraft in a 2B software configuration during the early stages of the program, Vice. Adm. Mat Winter, head of the F-35 joint program office, said Monday. It would take at least 150 modifications to bring each jet up to the 3F software standard associated with full combat capability.

The JPO is conducting a business case analysis to see whether it would be worth conducting the modifications or if that money would be better spent ramping up production and further modernizing the Block 3 jets. That could mean that a portion of the F-35 fleet will never be fit for combat, and could instead be used for testing or training.

Air Force Chief of Staff Gen. David Goldfein downplayed the situation, telling reporters at the Air Force Association annual conference that the service has had similar conversations in the past about other fighter jets.

“What you’re going to see is us continue to do a business case analysis of the cost to retrofit the older aircraft as we go forward. This is not a big dialogue,” he said Sept. 19. “We have actually had this dialogue with the F-16, we had this dialogue with the F-15, we had this dialogue with the F-22. We just haven’t had it for a while.”

In the case of the F-22, the service ultimately opted to keep a portion of its inventory at a lower software configuration, using those assets specifically for training. Today, about 36 F-22s remain in the Block 20 configuration, while 149 F-22s are combat-coded Block 30/35 jets.

Goldfein added that he would be engaged with others who are purchasing the F-35, such as his Marine Corps and Navy counterparts on the joint staff and international air chiefs, on how best to move forward.

The Pentagon’s independent weapons tester had warned in its 2015 report that modernizing earlier versions of the F-35 could prove too costly later on in the program, leading to a portion of the fleet that would never be upgraded.

“These modifications may be unaffordable for the services as they consider the cost of upgrading these early lots of aircraft while the program continues to increase production rates in a fiscally-constrained environment. This may potentially result in left-behind aircraft with significant limitations for years to come,” the report stated.