At the moment drones could fly only several minutes, but imagine if you get hours and hours of flight time, imagine if you get 5 kg of payload, this will be useful for thousands of purposes, from delivering humanitarian aid to package delivery.
Finally, we can get it. First hybrid system for drones was designed at NASA and it's really similar to what we are doing here (you can see the NASA system here:
Basically, it's an alternator connected to a gas motor, it is very similar to the system that is improved in your car to keep the lights on, the difference is that it's thous