Bertrand Piccard (R), pilot and president of Solar Impulse and Andre Borschberg (L), CEO and pilot of the company, congratulate German test pilot Markus Scherdel, after solar-powered Solar Impulse HB-SIA prototype airplane's first flight over Payerne April 7, 2010. The propeller plane, with a 61 metres (200 feet) wingspan, is powered by four electric motors and designed to fly day and night by saving surplus energy from its 12,000 solar cells in high-performance batteries. Wednesday's flight follows six years' work by 50 engineers and technicians led by Swiss adventurer Bertrand Piccard on the so-called Solar Impulse project. REUTERS/Christian Hartmann (SWITZERLAND - Tags: TRANSPORT ENVIRONMENT SCI TECH)