A solar-powered aircraft will on Thursday attempt an intercontinental flight from Switzerland to Morocco without using a drop of fuel.
If successful it will be the longest journey to date for the Solar Impulse after an inaugural flight to Paris and Brussels last year.
Organisers announced at the end of March that the 2500km trip will coincide with the launch of construction on a thermal plant in the southern Ouarzazate region of Morocco.
The trip will be a rehearsal for a round-the-world flight planned for 2014.
The aircraft, which has the wingspan of a large airliner but weighs no more than a saloon car, made history in July 2010 as the first manned plane to fly around the clock on the sun's energy.
It holds the record for the longest flight by a manned solar-powered aeroplane after staying aloft for 26 hours, 10 minutes and 19 seconds above Switzerland.
It also set a record for altitude by flying at 9235 metres.