TOKYO: A solar-powered plane took off from Japan on Monday on the seventh leg of its journey around the world, a trans-Pacific crossing expected to be the toughest part of the trip.

The Solar Impulse 2 left Nanjing, China, on May 31 for Hawaii, but was forced to cut short its bid a day later due to what pilot Andre Borschberg termed “a wall of clouds” over the Pacific and land in the central Japanese city of Nagoya.

This five-days-five-nights flight is a one-way ticket to Hawaii, say organisers

Its departure was postponed several times due to poor weather, once last week with the plane - which bears 17,000 solar cells across its wingspan - on standby at the end of a runway.

“This is a one-way ticket to Hawaii,” organisers said on their website today, eight hours after the plane’s pre-dawn departure. “Andre Borschberg ... must now see this five-days-five-nights flight through to the end.”

The plane took off from Abu Dhabi in March on the 35,000-km global journey. Overall, the trip was expected to span approximately 25 flight days broken up into 12 legs at speeds between 50 and 100 kph.

The plane has a wingspan as wide as the largest passenger airliner. Studies, design and construction took 12 years and a first version of the craft rolled out in 2009 broke records for heights and distances travelled by a manned solar plane.