Zero-fuel Solar Impulse plane begins last leg of global journey

CAIRO, July 24 (UPI) -- Solar Impulse, a zero-fuel plane circumnavigating the globe, is now on its last leg of its worldwide journey.

The plane left Cairo, Egypt and should reach Abu Dhabi, in United Arab Emirates within 48 hours, completing its flight around the world, BBC reported.

Pilot Bertrand Piccard's flight could go without a hitch, but his team is concerned the heat in the Middle East might affect the aircraft, which started its journey in March 2015. Piccard will likely spend most of the flight at high altitutdes using oxygen to breathe so he can avoid turbulence from the thermals. That will also mean the plane's motors will have to work harder to propel it forward. That requires Piccard to carefully manage the energy reserves in the plane's lithium polymer batteries so the aircraft can get through the night.

The single-seat plane left Cairo in the dark of night and could take as long as 72 hours to reach its final destination, SkyNews reported.

"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," Piccard said.

The pilot had shared duties with business partner and friend Andre Borschberg. The two had initially hoped to complete the trip last year, but weather hampered that effort. Then, the plane suffered battery damage over the western Pacific last summer, grounding the plane for 10 months.

Getting the plane back to Abu Dhabi will put closure on the pilot pair's 17-year effort to prove that a solar plane could make it around the world.

Piccard got the idea in 1999 when he made the first non-stop trip around the globe in a balloon.