An ambitious attempt to circumnavigate the globe in a solar-powered plane is facing a "moment of truth" after two weeks of bad weather that have left it stuck in Japan, its pilot said Tuesday.
With frustration starting to build a fortnight after Solar Impulse 2 made an impromptu landing in Nagoya, it was vital to keep a cool head about the best time to begin the next leg to Hawaii, Andre Borschberg said.
"This is the moment of truth for the project, it is the moment of truth for our team ... we want to be so cautious and not to make a stupid decision."
Solar Impulse set off from Abu Dhabi earlier this year in a multi-leg attempt to get all the way around the world using only the power of the sun.
However, the journey from China to Hawaii had to be cut short when meteorologists warned of a developing cold front over the vast Pacific Ocean.
Borschberg, 62, admitted members of the team "may be a little impatient" in their search for "a good weather window" that will allow them to undertake the lengthy crossing.
But "we don't want to take a risk in the sense of trying to gamble on the weather."
The plane, which has 17,000 solar cells and on-board rechargeable batteries, is expected to take at least five days and five nights of continuous flying to reach Hawaii. Its top speed is 140 kilometres (90 miles) an hour.
The flight will be the eighth and most ambitious leg of its record-breaking attempt to get around the globe.
If successful it will smash the 44-hour continuous flight record that the plane set from Nanjing, China, to Nagoya.
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.