Solar Impulse sets record but faces 'difficult' hours

Los Angeles

A solar-powered aircraft flying from Japan to Hawaii on the most perilous leg of a round-the-globe bid has beaten the record for the longest solo flight, organizers said Thursday.

But they admitted that veteran Swiss pilot Andre Borschberg is exhausted after more than four days of continuous flying, making the final 24 hours of flight particularly challenging. 

"UPDATE #PACIFIC: @andreborschberg is tired. W/ turbulence at 8'000 feet & a cold front close, SITUATION IS DIFFICULT," said a tweeted update from the mission control center (MCC) of the pioneering Solar Impulse 2 aircraft. 

"#MCC #solarTEAM is working hard to assess the situation & help @andreborschberg during this stressful period."

The plane is due to land Friday morning local time at Kalaeloa Airport on the main Hawaiian island of Oahu, some 20 miles (30 kilometers) west of Honolulu.

By 1930 GMT Thursday Solar Impulse 2 had traveled 86 percent of the way to the tropical US state, having flown 7,075 kilometers.

But it was in the process of crossing a cold front which requires Borschberg to navigate carefully, significantly increasing stress levels for the 62-year-old.

So far Borschberg has flown more than 97 hours -- easily beating the previous longest solo endurance flight, by Steve Fossett, who flew for 76 hours and 45 minutes in 2006.

The whole trip from Japan to Hawaii was expected to take 120 hours.