A red button is pictured on the control yoke in the cockpit of the solar-powered Solar Impulse 2 aircraft after a training flight at its base in Payerne November 8, 2014. The aircraft, which was unveiled April 9, weighs 2.4 tons with a wingspan of 72 meters (236 ft.) and more than 17,000 solar cells. The attempt to fly around the world in stages using only solar energy will be made from March 2015 starting from Abu Dhabi. REUTERS/Denis Balibouse (SWITZERLAND - Tags: TRANSPORT ENVIRONMENT SCIENCE TECHNOLOGY)