Battery-powered drones have limited range, David Hambling notes (in Swarm Troopers), but perching on power lines opens up the possibility of recharging by stealing electricity:
There are already several drones that can hook up to power lines line and recharge. Design Research Associates has developed such a system for small drones and a spin-off known as the “Bat Hook” for Special Forces. This really does look like something Batman would use – a small, sharpened boomerang with a line attached. Toss it over a power line and the sharp edge cuts through insulation. A device on the end of the line converts the high-voltage alternating supply into a regulated direct current for charging electronics. The Bat Hook can be popped off the line so it can be removed and reused.
This technology should be scaled up so that electric passenger planes can tether to specially built power lines connecting major cities. The insulation on the lines could be slitted so that a hook could slip under the insulation and glide across the wire.
I wonder how easy it is to pop off the line? I’m not messing around in any foreign electricity lines and risking electrocution.