On 7 July 2009, the world's first piloted aircraft able to take off using fuels cells as its only energy source – the motorised glider Antares DLR-H2 – made its maiden flight from Hamburg airport. The advantage of using fuel cells as a power source is that the only by-product is clean water. If the hydrogen used in the cells is produced using renewable energy, the motorised glider flies without any carbon dioxide emissions. Bild: DLR.