We have no flight-tracking system for the lower sky. There are rules and charts for keeping track of larger aircraft that carry human passengers and are piloted by humans onboard, but drones are small and fly low, which means we have to trust in drone pilot good behavior to keep drones away from risky places, like airports. Small drones, unlike other aircraft, don't broadcast their location, so tracking them in the sky is tricky. That's why the FAA is working with NASA to come up with an Unmanned Aerial System Traffic Management system. Or, essentially, air traffic control for drones.