Solar plane begins final flight

Solar Impulse 2, the world's first airplane flying on solar energy, is pictured en route to Ahmedabad March 10, 2015. The Swiss-built solar aircraft took off from Muscat in Oman earlier on Tuesday to begin the second leg of its epic journey. The unprecedented attempt at the first flight around the world seeks to prove that flying is possible without using fossil fuel. On its five-month journey of 35,000 km (22,000 miles), the engines will be powered only by solar energy. Two Swiss pilots, Bertrand Piccard and Andre Boschberg, will take turns at the controls in the tiny cabin for five consecutive days and nights in the air. REUTERS/Jean Revillard/Handout via Reuters (INDIA - Tags: TRANSPORT SCIENCE TECHNOLOGY ENVIRONMENT) ATTENTION EDITORS - FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS

The world’s largest solar-powered aircraft, Solar Impulse 2 has left the Egyptian capital, Cairo, on the last leg of its round-the-world tour, the BBC reported on Sunday.

According to officials, the aircraft should take about 48 hours to reach Abu Dhabi — the place it began the circumnavigation in March 2015.

“We thought it was going to be an easy flight because it’s always good weather between Egypt and Abu Dhabi across Saudi. But actually, it’s extremely difficult to find a good strategy,” the pilot Bertrand Piccard told BBC News before take off late Saturday night.

He added that the warmer, thinner air above the Saudi desert also means Solar Impulse’s motors will have to work harder to propel the vehicle forward.

This will require careful management of the energy reserves in the plane’s lithium polymer batteries, to be sure they can sustain the aircraft through the night hours, BBC quoted the pilot as saying.

The Solar Impulse has covered some 30,000 km in its quest to become the first plane to circle the world using no fuel, just the energy from the Sun.

The Cairo-Abu Dhabi flight marks the 17th and final segment in the journey, which has included crossings of the Pacific and Atlantic oceans.

Mr. Piccard has alternated pilot duties with his friend and business partner Andre Borschberg.