The Swiss-made solar-powered plane Solar Impulse 2 departs from Nanjing Lukou International Airport in Nanjing, capital of East China's Jiangsu province, May 31, 2015. The solar-powered plane left China for Hawaii on Sunday. It will fly across the United States and make several stops before finally reaching Abu Dhabi. [Photo/Xinhua]

NANJING - Swiss-made solar-powered plane Solar Impulse 2 departed from the eastern Chinese city of Nanjing on Sunday morning to fly across the Pacific, the toughest segment in its round-the-world trip.

Solar Impulse 2's departure from China to Hawaii at 2:40 am Sunday morning came more than a month after it landed in Nanjing on the night of April 21.

The plane delayed its originally planned departure from Nanjing on May 5 as its two pilots waited for the right weather conditions.

The journey from Nanjing to Hawaii is expected to take six days and six nights, with Andre Borschberg, 62, at the controls.

When he crosses the ocean, Borschberg will only be able to nap for 20 minutes at a time, the maximum amount of time the solar plane can navigate automatically.