Solar Impulse 2 has taken off on what is expected to be the final leg of its solar-powered round-the-world voyage. Today at 23:28 GMT (July 24, 1:28 am EET), the single-seater aircraft took off from Cairo International Airport with Bertrand Piccard at the controls.

After a ten day layover in Cairo due to pilot illness and poor weather, Solar impulse 2 is now on the 17th leg of its journey, which is expected to end in two days at the starting point in Abu Dhabi.

Tonight's takeoff is the latest in the circumnavigation that began in March 2015 to prove that an experimental solar-powered aircraft could circle the globe. If all goes well, it should cover the 1,471 mi (2,368 km) to the Al Bateen Executive Airport outside the capital of the United Arab Emirates by Tuesday morning.

However, mission control in Monaco points out that although the last leg is relatively short, it is still fraught with hazards. The summers in the region are extremely hot with temperatures on the design edge of the solar aircraft's systems. This will also produce flight hazards because high-altitude thermals and turbulences will require Piccrd to fly on oxygen at higher altitudes for extended periods of time.

"It's very emotional to take off from Egypt with Si2, given that I landed here in 1999 after accomplishing the first non-stop round the world balloon flight," says Piccard. "It's precisely here that started my dream of making another circumnavigation, but this time without fuel, only on solar power. I'm excited to come so close to the goal, but unfortunately there are still so many people we have to motivate before having a world running on the same clean technologies."

Solar Impulse