I agree with Cab on the turbulence issue. Having inflight refueled hundreds of times off a HC-130 I have experienced prop turbulence. But in this case I don’t believe turbulence was the issue as fighter appears to be approaching from above the B-17 and impacts fuselage from above and just behind the wings. Also it spy he brother formation as he is turning inside of the other aircraft in the formation. I have flown in numerous air shows during my 25 years flying in the Air Force. I know for a fact the before those guys fly there is a before flight briefing were the position of every aircraft in the formation, speed, each turn / maneuver is disused in detail so everyone knows what each aircraft is doing. I’m leaning more towards he had a medical issue and passed out.