The first night flight of a solar-powered craft in 2010 was followed by a first international flight in 2011, and first inter-continental flight in 2012.
Switzerland is home to several renewable energy projects, including the most advanced solar-powered aircraft, the Solar Impulse, which made its first international flight less than two weeks ago.
Speaking of sun-powered planes, the Solar Impulse just made its final test flight around the San Francisco Bay Area before embarking on a cross-country voyage next week.
And last year, defence firm Qinetiq flew a solar-powered plane for 54 hours, smashing the official world record for the longest-duration unmanned flight.