In the longest leg of its planned around-the-world flight, the Solar Impulse took off from Nagoya, Japan, and is now headed to Hawaii. The plane is powered solely by the sun's energy that's stored in batteries; the current trip is expected to last 120 hours — five days and five nights.

The plane is flying at 8,070 feet and moving at 29 knots. You can follow its progress over the Pacific Ocean on the project's website and on a live feed via YouTube.

André Borschberg, one of two pilots who take turns flying legs of the attempt to set a new solar flight record, took off in the wee hours of Monday morning (Nagoya time). He's not scheduled to land again until Friday morning (Eastern time).

The Solar Impulse left Nagoya after at least two other takeoffs were canceled over concerns about bad weather in the flight plan. The plane's window for taking off is fairly small. Given its large size and delicate structure, the Solar Impulse generally takes off from airports late at night, during cool and calm conditions.

The attempt at a fuel-free circumnavigation began in March; before arriving in Japan, the plane flew from Abu Dhabi to India, and China. Its organizers plan to fly from Hawaii to Phoenix before heading on to New York and then Europe.

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