I spent some time hanging out at an RC club in rural Connecticut that was co-located with a small airport. If you think they just flew their RC machines willy-nilly, you are dead wrong. There was strict coordination with flight control, and real airplanes would take precedence. Traffic was low enough that this worked out well in practice.

And I did in fact witness a jet-powered RC plane being flown there one weekend, which was quite impressive. At no time was a real airplane in danger of some kind of collision.

The point is, RC clubs like this one do think about this stuff, and they do take appropriate precautions.