TOKYO - A revolutionary solar- powered aircraft was past "the point of no return" and flying over the Pacific Ocean bound for Hawaii yesterday, on the most ambitious leg of its quest to circumnavigate the globe.
After a month of delays in Japan and a last-minute false start last week, mission controllers declared Solar Impulse 2 had at last taken off from the central Japanese city of Nagoya.
"No Way Back! This is a one way ticket to Hawaii," tweeted @solarimpulse, adding that pilot "Andre Borschberg has passed the point of no return and must now see this 5 days 5 nights flight through to the end."
About 12 hours after take-off, the plane was more than 1,000km into its 7,900km flight, according to the website Solarimpulse.com.
"We have to follow like a corridor with no clouds," mission initiator Bertrand Piccard said.
The eighth leg of the journey is considered the trickiest so far, with nowhere to land if things go wrong. In the worst-case scenario, that would mean Mr Borschberg ejecting from his super-lightweight cockpit with a parachute and a life raft.
He will inflate "the life raft and wait for another plane to bring... life support. And then the pilot can stay in this big raft for maybe three days until a ship can come and rescue him", Mr Piccard said.
Mr Borschberg, 62, has said he will keep in shape during his long solo flight by doing yoga, and will sleep 20 minutes at a time.
The featherweight flying machine was not supposed to land in Japan, but bad weather en route from Nanjing in China to Hawaii forced a diversion at the start of June. The plane had been stranded in Japan, with the crew scouring long-range forecasts for a favourable weather window.
Solar Impulse 2 has 17,000 solar cells and on-board rechargeable batteries with a top speed of 140km an hour. Its wingspan is longer than that of a jumbo jet, but it weighs only 2.3 tonnes - about the same as a car.
If successful, it will be the longest-duration solo flight in aviation history, as well as the furthest distance flown by a craft that is powered only by the Sun.