It's very light, it didn't fly very fast or very far, but the plane in the photo above made aviation history by making the first manned flight powered by a hydrogen fuel cell. The Boeing Research & Technology Europe team in Madrid, Spain, modified a two-seat Dimona motor-glider and installed a hybrid propulsion system based on a hydrogen fuel cell and lithium-ion batteries.
There were three test flights in February and March around the Ocaña airfield, south of Madrid.
During the flights, the pilot of the experimental airplane climbed to an altitude of 1,000 meters (3,300 feet) above sea level using a combination of battery power and power generated by hydrogen fuel cells. Then, after reaching the cruise altitude and disconnecting the batteries, the pilot flew straight and level at a cruising speed of 100 kilometers per hour (62 miles per hour) for approximately 20 minutes on power solely generated by the fuel cells.
Not exactly air-show material, and the more demanding take-off was done using help from the batteries, but it's a start.
Boeing is not expecting large passenger aircrafts to be powered by hydrogen fuel cells any time soon (see the second half of this post for our predictions on green(er) air travel), but they could be used in small manned and unmanned airplanes and serve as auxiliary power-generation units for large commercial airplanes.
You can see a video at the Boeing press release page.