Solar plane nears end of historic round-the-world trip

Abu Dhabi : Solar Impulse 2 was on Monday approaching the end of its epic bid to become the first sun-powered airplane to circle the globe without a drop of fuel to promote renewable energy.

When the experimental aircraft touches down in Abu Dhabi in the early hours of Tuesday it will cap a remarkable 42,000-kilometre (26,097 mile) journey across four continents, two oceans and three seas.

With Swiss explorer and project director Bertrand Piccard in the cockpit, the plane is due to land at Al-Bateen Executive Airport in the UAE capital where it launched its tour on March 9, 2015.

On Monday Solar Impulse 2 was flying over the Saudi desert north of Riyadh, heading towards the Gulf.

"After a turbulent night from extreme high temperatures, the sun rose above a desert of sand dunes above #SaudiArabia," Piccard said on Twitter.

Dubbed the "paper plane", Solar Impulse 2 is circumnavigating the globe in stages, with 58-year-old Piccard and his compatriot Andre Borschberg taking turns at the controls of the single-seat aircraft.

It took off from Cairo on its final leg early on Sunday, having previously crossed Asia, North America, Europe, and North Africa.

Borschberg, 63, smashed the record for the longest uninterrupted journey in aviation history with the 8,924-kilometre (5,500-mile) flight between Nagoya, Japan and Hawaii that lasted 118 hours.

No heavier than a car but with the wingspan of a Boeing 747, the four-engine battery-powered aircraft relies on around 17,000 solar cells embedded in its wings.

Its broad wings and light weight make it particularly sensitive to turbulence.

The plane has clocked an average speed of 80 kilometres (50 miles) an hour.