A solar-powered plane's flight across the Pacific Ocean was going smoothly as it gets closer to a stop in Northern California.
The Solar Impulse 2 picked up a strong tail wind before sunset on Friday and was cruising at 150 kph, or about 93 mph. It was expected to arrive in the San Francisco Bay area by Saturday evening.
The aircraft started its around-the-world journey in March 2015 from Abu Dhabi, the capital of the United Arab Emirates, and made stops in Oman, Myanmar, China and Japan. It's on the ninth leg of its circumnavigation.
Pilot Bertrand Piccard marveled from his plane as it cruised over the Pacific at about 16,000 feet with a nearly-full battery, according to the website documenting Solar Impulse 2's journey.
The Solar Impulse 2 airplane, piloted by Bertrand Piccard takes gains altitude after taking off from Kalaeloa Airport, in Kapolei, Hawaii on April 9, 2016 for a test and training flight. Solar impulse 2 is attempting to be the first solar powered airplane to fly around the world without using fuel. (Photo: Eugene Tanner/AFP via Getty Images)
He told his wife he could see the full moon's reflection on the ocean.
"For now I will say goodnight from the middle of the ocean,'' Piccard said during a brief conversation streamed live on the website. "This is an extraordinary experience.''
— SOLAR IMPULSE (@solarimpulse) April 21, 2016
Earlier, he exchanged pleasantries with UN Secretary-General Ban Ki-moon, who hailed Piccard's pioneering spirit as "inspirational,'' telling him he was making history.
Piccard responded that Ban, too, was making history by having just presided over the signing of a climate agreement supported by representatives of 175 nations.
"What you are doing today in New York, signing the Paris agreement, is more than protecting the environment, it is the launch of the clean technology revolution,'' Piccard said.
The trans-Pacific leg of his journey is the riskiest part of the solar plane's global travels because of the lack of emergency landing sites.
"What you are doing today in New York, signing the Paris agreement... is the launch of the clean technology revolution.''
After uncertainty about winds, the plane took off from Hawaii on Thursday morning and was on course to land in Mountain View, California, over the weekend. The crew that helped it take off was clearing out of its Hawaiian hangar and headed for the mainland for the weekend arrival.
At one point passengers on a Hawaiian Air jet caught a glimpse of the Solar Impulse 2 before the airliner sped past the slow-moving aircraft.
The Solar Impulse 2 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.
Piccard, said the destination in the heart of Silicon Valley is fitting, as the plane will land "in the middle of the pioneering spirit.'' Piccard's co-pilot Andre Borschberg flew the leg from Japan to Hawaii.
The team was delayed in Asia, as well. When first attempting to fly from Nanjing, China, to Hawaii, the crew had to divert to Japan because of unfavourable weather and a damaged wing.
Solar Impulse 2 pilot Bertrand Piccard speaks on Dec. 3, 2015 during a conference as part of the World Climate Change Conference 2015 (COP21), in Le Bourget, on the outskirts of Paris. (Photo: Patrick Kovarik/AFP via Getty Images)
A month later, when weather conditions were right, the plane departed from Nagoya in central Japan for Hawaii.
The plane's ideal flight speed is about 45 kph, or 28 mph, though that can double during the day when the sun's rays are strongest. The carbon-fiber aircraft weighs more than 5,000 pounds, or about as much as a midsize truck.
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. The plane runs on stored energy at night.