John, doesn't that depend on the drone? There are some amazing zoom lenses today. And if it's a government drone, who knows? Black helicopters are so passe. :-)
I once watched a car chase of a stolen Charger, the helicopter couldn't keep up with him. But they could still follow the car on the highway from over 10 miles away. PS, the police caught him, had another helicopter finally find after a jog off the side of the highway.
Mikek