A SWISS solar plane pilot has embarked on the longest leg of the first attempt to fly around the world without a drop of fuel.
André Borschberg took off from Nanjing, China, in the Solar Impulse 2 for a flight across the Pacific Ocean, powered only by the Sun, that is expected to take at least 130 hours.
The journey started in March in Abu Dhabi, and the solar plane has stopped in Oman, India, Burma and China. The 5,079-mile flight from Nanjing to Hawaii is the seventh of 12 flights and the longest and most dangerous.
Mr Borschberg and another Swiss pilot, Bertrand Piccard, have been taking turns flying the single-seater plane during the journey, which is to promote renewable energy use.
The experimental aircraft has a wingspan bigger than a jumbo but weighs little more than a large car.
It is likely to take Mr Borschberg five to six days of continuous flight to reach his central Pacific destination.
He will try to stay awake for much of that time, taking only short catnaps, and his progress will be monitored from a control room in Monaco. Meteorologists and flight strategists will constantly update him on the best route to follow.
If successful, this stretch of Solar Impulse’s round-the-world trip will be the longest solo flight in history.
The project made steady progress after starting out from Abu Dhabi in March, but was held up for more than a month on China’s east coast waiting for the right weather conditions over the ocean.
Solar Impulse needs not only favourable winds to help push it forward, but also clear skies to enable its 17,000 wing-mounted photovoltaic cells to achieve peak performance. These cells must have the vehicle’s lithium-ion batteries fully topped up at dusk to sustain flying through to dawn the next day.
Mr Borschberg is a highly experienced pilot, and, as a trained engineer, is completely familiar with the plane’s systems.
Nonetheless, he is in no doubt how tough the mission will be.
“It’s more in the end about myself; it’s going to be an inner-voyage,” he said before departure. “It’s going to be a discovery about how I feel and how I sustain myself during these five or six days in the air.”
Mr Piccard said: “There’s one pilot at a time, so the pilot needs to do everything on his own. And it’s a very large aeroplane, big wingspans, sensitive to turbulence, flying quite slow. So sometimes it’s difficult to handle when the air moves.
Before take-off, Mr Borschberg, 62, said: “This is the moment of truth.”
He said he and Mr Piccard’s embraced a vision 16 years ago “to change our mindset regarding the enormous potential of clean technologies and renewable energies”.
After Hawaii, Mr Piccard will pilot the aircraft on to Phoenix, in the US state of Arizona.