Solar Impulse 2 is scheduled to taxi out along the runway in Nagoya, central Japan, in the small hours of the morning, to begin its hazardous trip across the Pacific Ocean, a distance expected to take at least five days and five nights of continuous flying.
"Solar Impulse will attempt to fly to Hawaii tomorrow, at 2:30am local time," the team said.
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, China, to Hawaii forced a diversion at the start of June.
A chance to do so presented itself today.
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"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 tonight's flight.
Winds and turbulence tend to be calmer in the very early hours of the morning, Solar Impulse team spokeswoman 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."
"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 cubic metre (130 cubic foot) cockpit for long stretches of time 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 plane has 17,000 solar cells and on-board rechargeable batteries. Its top speed is 140 kilometres (90 miles) an hour.