German test pilot Markus Scherdel steers the solar-powered Solar Impulse 2 aircraft during its maiden flight at its base in Payerne June 2, 2014. The aircraft, which was unveiled on April 9, has a wingspan of 72 metres (236 ft), and weighs 2.4 tons, bearing in total more than 17,000 solar cells. The attempt to fly around the world in stages using only solar energy will be made in 2015.DENIS BALIBOUSE/Reuters