[zelphirkalt]

I guess the only solution then is to already have people in places where it counts. I would suspect military bases have more than enough people. But then again the drones can just fly too high, at which point it becomes a cost/benefit tradeoff, or futuristic laser weapons.

[exDM69]

Anything involving people on the ground is just too slow.

It takes radars, interceptor drones, sensor networks, etc. Stuff like this is in active development but not widely deployed yet.