Solar Impulse confirmed for take off from Japan early on Wednesday

Solar-powered airplane Solar Impulse 2 sitting in the mobile hanger at the Nagoya airport in Nagoya, central Japan, on June 3, 2015.
Solar-powered airplane Solar Impulse 2 sitting in the mobile hanger at the Nagoya airport in Nagoya, central Japan, on June 3, 2015. PHOTO: AFP

NAGOYA, Japan (AFP) - A solar plane that has been trapped in Japan for three weeks will take off early on Wednesday, the team confirmed, on the most challenging leg of an attempt to circumnavigate the world without using fuel.

Solar Impulse 2 will taxi out along the runway at Nagoya in central Japan in the small hours of the morning to begin its hazardous trip across the Pacific Ocean, expected to take at least five days and five nights of continuous flying.

"Solar Impulse will attempt to fly to Hawaii on Wednesday, June 24th at 2.30am local time," the team said. "We see no red flags to attempt a first in history to reach Hawaii," #solarimpulse tweeted later in the day.

The featherweight flying machine was not supposed to land in Japan on its multi-leg trip around the globe, but bad weather en route from Nanjing in China to Hawaii forced a diversion at the start of June. Ever since, the crew has been scouring long-range forecasts for an opportunity to restart its record-breaking journey.

A chance to do so presented itself on Tuesday.

"We finally feel like we have a window to Hawaii in front of us. It will be confirmed at 12.00PM UTC! (GMT)" tweeted pilot Andre Borschberg.

Borschberg, who flew for 44 hours to get to Nagoya, will be back at the controls for the flight early Wednesday.

Winds and turbulence tend to be calmer in the very early hours of the morning, Solar Impulse team spokesman Elke Neumann told AFP, making this time ideal for takeoffs.

"The batteries are full so the plane can fly any time," she said. "Since the sun comes up very early in Japan, we are flying early... we fly much earlier, so we have much more time in the air."

Mr Borschberg, a 62-year-old Swiss, will keep in shape during his long solo flight by doing yoga.

"I train special postures, which I do every day in the cockpit... to keep the right mental attitude," he told AFP earlier this month.

"Breathing can help... yoga is much about breathing."

But he admitted that being cooped up in the 3.8 cu m cockpit for long stretches was a challenge.

Solar Impulse 2 set off from Abu Dhabi earlier this year in a multi-leg attempt to get all the way around the world without a single drop of fuel.

The trip to Hawaii will be the eighth and most daunting leg of the circumnavigation.

The plane has 17,000 solar cells and on-board rechargeable batteries. Its top speed is 140 kmh.

Its wingspan is longer than that of a jumbo jet, but it weighs only 2.3 tons - about the same as a car.

The plane is the successor to Solar Impulse, which managed a 26-hour flight in 2010, proving its ability to store enough power in lithium batteries during the day to keep flying at night.

Ridiculed by the aviation industry when it was first unveiled, the venture has since been hailed around the world, including by UN chief Ban Ki Moon.