Photos: Flying on a wing and a battery

Within two years, Falx Air Vehicles of Staffordshire, England, is planning to commercialize tilt-rotor aircraft with hybrid-electric motors and built-in solar panels. An aerial ambulance such as this would be powered by both photovoltaics and a combustion engine.

Engineers have looked into placing solar panels on airplane wings, but found the additional drag a barrier.

As with cars, the next step toward greening air travel could involve hybrid-powered craft.