The low mass of airplane prop blades and the distance the planes are from the pilots ensure that a prop blade can't reach anyone. The air resistance would slow it way down before it came anywhere near anyone.

At a guess, I'd say you'd have to be within maybe 20feet for a typical combat airplane prop to still have enough force to actually hurt you if it let go. So, be careful in the pits, but once launched, nothing to worry about.

I've seen plenty of botched launches where the prop hits the ground then shoots up in the air. The prop never carries very far. Also, the prop arc is parellel and away from the pilots, so the blades go up or to the sides, but not back towards anyone. A helicopter has the entire pit area in the prop arc.

Helis are also a lot more sensitive to being a little out of wack. Even a small tap will tear up the rotors, while with airplanes, we routinely glide back in safely missing large portions of our airplanes, or with sizeable dents in the wings. Or at least do a controlled ditch out in the weeds.

Overall, it's a silly concept. I wouldn't want to be around if someone did it, but I'd sure like to see the video (as long as no one got hurt).