The F-35 has been proven in simulations with aggressor squadrons. The Air Force does that all the time: real aircraft in the air, real pilots, real weapons, they just don't actually shoot them for obvious reasons. But they have other ways of simulating kills.

https://www.businessinsider.com/f-22-pilot-describes-going-u...

Here's what a F-22 pilot (!) had to say about the F-35.

"It is challenging, even flying the Raptor, to have good [situational awareness] on where the F-35s are," he said.

Bowlds said that inserting F-35 aggressors into Red Flag made things "more challenging because there is a little bit of an unknown in terms of what they are going to be able to do."

Additionally, "red air detects are happening at further ranges," Bowlds explained. "It inherently poses more of a threat to allied blue-air forces than older aggressors," such as the fourth-generation F-16s.

The F-35s "have better detection capabilities kind of against everybody just because of their new radar and the avionics they have," he said. "It definitely adds a level of complexity."