Swiss explorers and pilots Andre Borschberg and Betrand Piccard announced Friday the would-be first plane to travel around the world only powered by solar energy, will take off for Hawaii from Nanjing, China as soon as Monday.

Borschberg will pilot the Solar Impulse 2 for the five-day flight. The Solar Impulse 2 crew said, depending on weather conditions, the plane will land at the Kalaeloa Airport in West Oahu on May 9. 

"Crossing the Pacific in Si2 is an ultimate test of endurance," said Solar Impulse in a news release. Borschberg will endure up to five consecutive days and nights of highly demanding conditions — sleeping only 20 minutes every few hours and existing in a space slightly larger than your average coat closet, the news release said. “Extreme weather and the unknowns inherent in pushing the boundaries of technology will combine to make this attempt a unique and unpredictable test of man and machine.”

Solar Impulse 2 departed March 9 from Abu Dhabi for the planned 25,000-mile trip around the world.  

The take-off from China and journey will be broadcast live at www.solarimpulse.com.