Two T-100's (Raytheon's T-X candidate) in formation flight (PRNewsFoto/Raytheon Company)

Holmes mentioned that perhaps the future trainer -- known as T-X -- could be morphed into a CAS platform but warned that it would be premature to add that requirement at this time.

"We're really careful with the T-X requirement because if we add requirements to T-X now, then it could become unaffordable and we can't replace the trainer role that we need it to replace," Holmes said. "There is an option down the road that you might take the airframe that's designed for T-X and use it for some other use, we have some money in our budget that will let us do the studies to do that."

But the most definitive admission of the folly of trying to force the F-35 into the CAS role came from Air Force Vice Chief of Staff Gen. David Goldfein last month. "I would never look at you and tell you, 'Hey, the replacement, one-for-one, for the A-10 is the F-35,'" Goldfein said.