In a comprehensive article published on Inc, the author calculated that the flying time and weight carrying capabilities exclude drones from being able to deliver over long distances. Based on a single battery charge and carrying a weight, current drone technology cannot cover much distance, reducing their usefulness for delivery in anywhere other than metropolitan areas that are near a delivery depot.
With the PROWL system, flight paths can planned to maximise distance covered in the least amount of time – by navigating around and avoiding objects and hazards. If drones were able to fly from a depot to an elevated charging station (such as on top of a building), and then fly on to their destination, all without a human pilot and avoiding known objects that could interfere with their flight path.