The Solar Impulse prototype HB-SIA took off this morning for what is intended to be its first night flight using only the power of the sun.
HB-SIA took off from Payerne air base in Switzerland at 07:51 local time with the project's co-founder and chief executive André Borscherg on board. It will spend the day ascending to an altitude of 8,500m (27,900ft) while the sun charges its batteries ahead of the planned night flight.
About two hours before sunset the sun's rays will no longer be strong enough to charge the prototype's solar cells, at which point it will begin a slow descent with the aim of reaching an altitude of 1,500m by 23:00 local time. The hope then is that it will be able to continue flying through the night using the energy stored in its batteries, landing back at Payerne on Thursday morning.
If the mission proves successful, the team behind the project says it will mark the "longest and highest flight" ever made by a solar aircraft.
The Solar Impulse project has been under development for seven years under the guidance of co-founder and balloonist Bertrand Piccard. The HB-SIA prototype is made entirely of carbon fibre and has a wing span of 63.4m. More than 12,000 solar panels built into the wing supply the energy needed to power its electric engines and charge its lithium-polymer batteries.
Piccard says the aim of the mission is to "demonstrate the potential of renewable energy and clean technologies".