A solar-powered Swiss airplane is scheduled to touch down in Hawaii Friday after a record-breaking flight across the Pacific Ocean, the riskiest leg of its 35,000-kilometer trip around the world without a drop of fuel. 

Solar Impulse 2 pilot Andre Borschberg has now beaten the previous longest solo piloting record that was held by American adventurer Steve Fossett.

Borchberg has taken 20-minute naps during the journey in the unpressurized cockpit while the aircraft was on autopilot.

Si2 flew out of Nagoya, Japan early Monday after an unscheduled month-long stop.  The aircraft was diverted to Nagoya because of bad weather at the beginning of June on its trip from Nanjing in eastern China to Hawaii.  Its final destination is Abu Dhabi.

Si2 is the brainchild of two Swiss scientists, Borschberg and Bertrand Piccard.  It took them 12 years to build the aircraft.