Swiss pilot Andre Borschberg has begun his bid to cross the Pacific, from China to Hawaii, in the zero-fuel Solar Impulse aeroplane.
The experimental aircraft, which has a wingspan bigger than a jumbo but weighs little more than a large car, left Nanjing at about 18:40 GMT.
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.
His progress will be monitored the entire way from a control room in Monaco…
The journey is the seventh leg in the single-seat, propeller-driven aircraft’s quest to circumnavigate the globe using just the energy of the Sun…
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 told the BBC 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.”…
If he succeeds in reaching Kalaeloa airport, he will set several aviation records – not least the longest-duration journey for a single-seater plane.
And then – he will carry on to North America, to Europe, and back to AbuDhabi.