You are right, power/weight ratio is important. I've seen news pop up in the last 12 months of fuel cell powered drones with several hours flight time (compared

You are right, power/weight ratio is important. I've seen news pop up in the last 12 months of fuel cell powered drones with several hours flight time (compared to under an hour with li-ion batteries) so I'm assuming they can push out enough power for a multirotor for decent lift without weighing too much. Fixed wings should definitely see good gains, as it requires less power to fly than multirotors. I haven't followed it closely but 5-10x flight times vs li-ion sounds realistic considering the energy density of hydrogen. http://www.hes.sg/ http://www.hes.sg/