During the test flights, the two-seater plane, based on a modified motorised glider, climbed to an altitude of 1,000m using a combination of battery and fuel cell power. At the cruise altitude, the batteries were disconnected, and the craft flew level at a speed of 100km/h for around 20 minutes, powered solely by the fuel cells.

The plane, which has a 16.3m-wide wingspan, has been developed over the past five years by a team lead by Boeing Research & Technology Europe. The lightweight,high-torque electric motor and controller were supplied by US-based UQM Technologies, while the fuel cell power system was supplied by Intelligent Energy, based in Loughborough, UK.

Boeing suggests that fell cells could be exploited commercially to power small manned and unmanned aircraft. Although it does not believe that fuel cells will ever provide primary power for large passenger planes, it says that fuel cells could be used in secondary power-generation applications such as auxiliary power units.

Fuel cells are electrochemical devices that convert hydrogen directly into electricity and heat. Water is the only exhaust product.