Solar plane slowly soaring from Hawaii to California

The plane was cruising over the cold northern Pacific late Thursday at about 20,000 feet with a nearly-full battery as night descended, according to the website that's documenting the journey of Solar Impulse 2.

At one point the plane was passed by a Hawaiian Air jet whose passengers caught a glimpse of the Solar Impulse 2 before the powerful airliner left the slow-moving aircraft behind.

The aircraft landed in Hawaii in July and was forced to stay in the islands after the plane's battery system sustained heat damage on its trip from Japan.

The trans-Pacific leg is the riskiest part of the plane's global travels due to the lack of emergency landing sites.

The wings of Solar Impulse 2, which stretch wider than those of a Boeing 747, are equipped with 17,000 solar cells that power propellers and charge batteries.