The problem is that you have to have heavier batteries for longer flight time, and then you need more power to lift that extra weight, so more power needed, so

The problem is that you have to have heavier batteries for longer flight time, and then you need more power to lift that extra weight, so more power needed, so more battery needed. It's a vicious cycle. I'm sure there's some rule or law about it. And unlike normal aircraft fuel, battery-powered drones don't get lighter during the flight. Batteries weight the same charged or not.