The Solar Impulse aircraft landed at Madrid-Barajas Airport at 1:19 a.m. Saturday, 17 hours after taking off from Rabat on its return trip to Switzerland "without using a drop of fuel" and flown exclusively with solar energy.

This is the second time that the solar-powered aircraft has landed at Barajas, following the stopover it made at the Madrid airport last May 25 for maintenance work on a flight it was making from Switzerland to Morocco.

The Solar Impulse was scheduled to reach Barajas in the wee hours last Tuesday, but a sudden change in the weather kept it from taking off from Rabat, since the aircraft only weighs 1,600 kilos (1 3/4 tons), though it has the same wingspan as an Airbus, which makes it very dependent on winds and air currents.

Organizers of the Morocco-Switzerland flight have said that, until it took off before dawn this Friday from Rabat, the aircraft had flown some 4,000 kilometers (2,500 miles).

Right on schedule, the prototype, created by Bertrand Piccard and Andre Borschberg, flew at sundown Friday over Toledo - the province and its like-named capital near Madrid - and reached Madrid-Barajas before midnight, but was unable to land for several hours so as not to interfere with the ordinary operations on the runways.

Piccard and Borschberg began this adventure seven years ago and made the first trial flight in 2009.

A year later, the Solar Impulse made its first real flight and was able to remain in the air day and night for 26 hours without any kind of fuel.

The 12,000 photovoltaic cells that cover its wings absorb solar energy and transfer it to the aircraft's four batteries, which allow it to fly for up to five hours.

The Solar Impulse's flight to Rabat came in answer to an invitation by Morocco's Solar Energy Agency, which plans to build five solar parks by 2020 with a capacity of 2,000 megawatts to generate a significant part of the nation's electricity.

During their stay in Madrid last May, the promoters of the flight said that the goal of their adventure was to show that "dreams are possible" and that a world powered by renewable energy "is a better world." EFE