Solar Impulse 2 sets off for Abu Dhabi on the final leg of its epic global journey

Solar Impulse took off from Cairo, and is headed toward Abu Dhabi for its final leg on the Round The World journey. Credit: Solar Impulse/Revillard

Solar Impulse 2 began the final leg of its incredible fuel-free round-the-world journey when it took off from Egypt Saturday.

Piloted by Bertrand Piccard, the solar-powered plane left Cairo International Airport at 7:28 p.m. EDT and is expected to arrive at Al Bateen Executive Airport in Abu Dhabi Monday after a flight of about 48 hours.

“Trying to rest in #Si2 after taking off from Cairo. Excited to attempt the final leg of the round-the-world flight,” Piccard tweeted late Saturday.

The final leg, however, poses major challenges as Solar Impulse 2 flies through the heat of the Middle East. The region’s current high temperatures will test the plane’s technology to the limits and can cause thermals and turbulence, even at high altitudes, according to the Solar Impulse team.

A larger version of a single-seat prototype that first flew six years ago, Solar Impulse 2 is made of carbon fiber and has 17,248 solar cells built into the wings that supply the plane with renewable energy, via four motors. The solar cells recharge four lithium polymer batteries, which provide power for night flying.

Solar Impulse Chairman Bertrand Piccard has taken turns with his fellow Swiss pilot Andre Borschberg to fly the single-seater plane around the world.

Piccard was at the controls when Solar Impulse 2 became the first solar-powered plane to cross the Atlantic last month after a flight of 71 hours and 8 minutes.

The flight from Cairo to Abu Dhabi is the 17th leg of the global journey, which began when the plane flew from Abu Dhabi to Oman in March 2015. Borschberg broke a number of records on the eighth leg of Solar Impulse’s 2 journey, landing in Hawaii on July 3, 2015 after an incredible 4,480-mile, 118-hour flight from Japan. The journey shattered the record for longest solar-powered flight in terms of distance and duration. Borschberg also broke the record for longest non-stop solo flight without refueling, which previously stood at 76 hours and 45 minutes.

However, the following leg – from Hawaii to California, was delayed for nine months while the Solar Impulse team repaired damage to the plane’s batteries sustained on the journey from Japan.

The plane has traveled more than 25,700 miles since setting off on the first leg of the trip and has racked up over 509 hours of flight time.

The solar plane’s adventure proves the vast potential of renewable energy, according to Piccard. “Clean technology is a huge opportunity that will create jobs, make profits and protect the environment,” he told FoxNews.com during an in-flight interview earlier this year.

Prior to its flight from Cairo to Abu Dhabi, Solar Impulse 2 made stops in Oman, India, Myanmar, China, Japan, Hawaii, California, Phoenix, Tulsa, Dayton, Lehigh Valley, New York and Seville.

Follow James Rogers on Twitter @jamesjrogers

The Associated Press contributed to this report.