A sun-powered plane made a successful test flight on Monday, clearing a vital hurdle towards its goal of a round-the-world trip next year, its pilot and mission chiefs said.
Solar Impulse 2 carried out a flight lasting two hours and 15 minutes, half an hour longer than scheduled, German test pilot Markus Scherdel said.
"Everything worked as expected," Scherdel told a press conference at an air base in Payerne, central Switzerland.
"Of course, we have to do more testing, but it's a good start and I'm looking forward to flying the airplane the next time."
Built from carbon fibre, the 2.3-ton plane has four 17.5-horsepower electrical motors powered by 17,248 solar cells studding its fuselage and 72-meter (234-feet) wingspan -- as long as that of an Airbus A380.
It is the successor of Solar Impulse, a record-breaking craft that in 2010 notched up a 26-hour flight, proving its ability to store enough power in lithium batteries during the day to keep flying at night.
The forerunner was put through its paces in Europe, crossed the Mediterranean to reach Morocco and traversed the United States last year without using a drop of fossil fuel.
The goal with Solar Impulse 2 is to fly non-stop for more than 120 hours -- five days and five nights -- enabling it to cross the Pacific and Atlantic legs of its global mission.
The operation in March 2015 will circle the globe eastwards, making numerous stops on the way.
It will start in the Gulf, to benefit from the Middle East's low-cloud conditions.