It didn’t use a drop of fuel.
More than a year into its journey, the Solar Impulse 2 completed the final leg of its global trek, taking off from Cairo and landing in Abu Dhabi where its historic journey first began. The solar powered plane has already completed the most challenging parts of its voyage but as Engadget points out, but these final days may have been the most-remembered as the world tuned in to watch history being made with the first globe trotting, fuel free flight in history.
Solar Impulse 2 began its journey in March 2015 from Abu Dhabi and in turns has been flown by by Swiss aviators Andre Borschberg and Bertrand Piccard. "Just took off from Cairo to achieve the 1st round-the-world solar flight. A dream I have since 1999," Piccard tweeted after the Impulse took flight.
The pilots were forced to endure long stints in the plane’s tiny cockpit space, oftentimes at thousands of feet above the Pacific Ocean. The plane itself only weighs about as much as a compact car, but can reach heights of nearly 30,000 feet, but treks along at relatively pedestrian speeds of 30-60mph on average. During the day, 17,000 solar cells take in energy from the sun, which is then stored in batteries that power the plane at night.
"The project is a big promotion of clean technologies around the world and the legacy of Solar Impulse is the created international community," Picard told Reuters.