Solar Impulse 2 will be stuck in Japan for at least a week, its pilot has said, after it sustained damage to its delicate wing following an impromptu landing in the country.

The plane was en route from China to Hawaii, in the most ambitious leg of a record-breaking attempt to circumnavigate the globe using only the power of the sun.

But mission controllers forced the high-tech aircraft to land in Nagoya on Monday, as a burgeoning cold front over the Pacific was blocking its path to the US islands.

Gusts of wind have since damaged the left aileron -- the moving hinge on the trailing edge of the wing that controls the plane's roll.

"It will take about one week for us to repair," pilot Andre Borschberg told reporters in Nagoya late Wednesday. "There is a small damage, it's nothing major."

The seventh leg of the aircraft's epic mission was intended to be the 8,500 kilometres (5,250 miles) from Nanjing, China, to Hawaii -- a journey set to take six days and six nights of non-stop flight.

In footage posted on the project's website, mission initiator Bertrand Piccard said exposure to the elements had been the problem.

"Before the team at Nagoya airport could inflate the mobile hangar, the wing had to be protected with a cover for the rain and the sun," he said.

"There were so much wind and gusts that this cover started to shake on the wing and damaged an aileron on the trailing edge of the wing.

"This of course will be repaired, the technical team already started to build some spare parts but it will keep us on the ground for at least one week before we can carry on and André to fly to Hawaii.

"It's not a big issue for the project itself but it's a little additional delay," Piccard said.

On a positive note, Piccard tweeted: "Being in Nagoya with #Si2 is the perfect opportunity to introduce our movement #futureisclean in Japan!"

The plane's journey is part of a drive to promote the use of sustainable energy.
Source: AFP