SAN FRANCISCO, CA - APRIL 23: In this handout image supplied by Jean Revillard, Solar powered plane 'Solar Impulse 2', piloted by Swiss adventurer Bertrand Piccard, flys over the Golden Gate bridge in San Francisco, after a flight from Hawaii during its circumnavigation, before landing at Moffett Airfield in Mountain View in Silicon Valley, on April 23, 2016 in San Francisco, California. The Solar Impulse 2 is equipped with 17,000 solar cells, has a wingspan of 72 metres, and yet weighs just over 2 tonnes. (Photo by Jean Revillard via Getty Images)