A pioneering plane attempting to circumnavigate the globe powered only by the sun took off in China early Tuesday for the next stage of its journey, organisers said.

The Solar Impulse 2's departure from Chongqing came after repeated meteorological delays and one of its co-pilots returned to Europe to be treated for migraine.

With pilot Bertrand Piccard at the controls, the plane took off at 6:08 am (2208 GMT Monday), heading for the eastern city of Nanjing, organisers said in a statement. The 1,190 kilometre flight was expected to take 20 hours.

The Solar Impulse 2 arrived at Chongqing airport from Myanmar on March 31.

It had been due to make a brief stop in the southwestern Chinese city and quickly travel on to Nanjing, but was held up by weather and safety concerns.

Chongqing, on the Yangtze river, is notoriously foggy but Solar Impulse 2 spokesman Marc Baumgarten said the initial delay was due to "cross winds which are covering the entire country".

Another departure attempt on April 16 was foiled "due to a narrow window for the landing in Nanjing", according to an update last week on the solar plane's Twitter account.

One of the co-pilots, Andre Borschberg, is also being treated in Switzerland for migraine problems.

"It was necessary for me to achieve detachment, to take a break in order to ensure the future of the project," Borschberg wrote in a Twitter update Monday.

The team behind Solar Impulse 2, which has more than 17,000 solar cells built into its wings, hopes to promote green energy with its round the world attempt.

The plane is the successor of Solar Impulse, which notched up a 26-hour flight in 2010, proving its ability to store enough power in lithium batteries during the day to keep flying at night.

On a previous circumnavigation, Piccard passed over China in a specially designed balloon, but only after he personally negotiated conditions requiring the craft to avoid large swathes of the country.

Ridiculed by the aviation industry when it was first unveiled, the Solar Impulse venture has since been hailed around the world, including by UN chief Ban Ki-moon.

The plane's maiden global circumnavigation began in Abu Dhabi and is scheduled to take in 12 stops, with a total flight time of around 25 days spread over five months.