An airplane powered by the sun is scheduled to land in Hawaii after a five-day journey over the Pacific Ocean.

The flight from Japan is the longest leg of the around-the-world voyage planned by two Swiss pilots who have been taking turns flying the single-seat airplane. It is also the riskiest because the plane has nowhere to land in an emergency.

The aircraft is scheduled to land at a small airport outside Honolulu about 6 a.m. (9 a.m. PDT) Friday. Flight officials say the aircraft was arriving in the Hawaii area earlier but would fly in a holding pattern until the scheduled landing time.

The pilots aim to create awareness about replacing fossil fuels with clean technologies.

Solar Impulse 2 took off from Abu Dhabi in March. The wings of the carbon fiber aircraft have more than 17,000 solar cells.