An electric, fixed-wing UAV, less than 3 kg, capable of flying up to 24 hours using a readily available fuel will revolutionize the UAV sector, and enable the proliferation of such systems. Small, long endurance UAV system could perform missions previously only possible with airplanes, helicopters and large UAVs, but at a fraction of the cost, and with much higher mission flexibility and availability. The key performance parameters of these UAV systems are: low weight [no need for take-off and landing infrastructure], electric propulsion [robustness, energy efficient and low noise signature], and a fuel-cell power system [long endurance].