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A new type of airplane is being flown around the world. It is powered by the sun, also known as solar-powered. There are two pilots flying this special plane.
The pilots said their plane, which is called Solar Impulse 2, shows the importance of renewable energy. Renewable energy is energy from a source that people can use over again, such as sunlight, wind or rain. Most aircraft uses gasoline, or jet fuel as its energy. The fuel comes from oil and it can only be used once.
Burning oil is also harmful for the planet and leads to global warming. This is the heating of the planet.
Bertrand Piccard is one of the pilots. The two pilots take turns flying the plane. Piccard flew across a big part of the Pacific Ocean in the solar-powered plane by himself. He slept only 20 minutes at a time inside the plane's tiny control center. It has no heat or air conditioning. He also had to talk with the control center in Europe.
"There are a lot of things to do," Piccard said. Still, he says he enjoys it.
The plane's flight speed is about 28 miles per hour. It can go twice as fast during the day when the sun is most strong. The airplane weighs more than 5,000 pounds. That is about as much as a medium-size truck.
The plane has 17,000 tiny machines that capture the light from the sun. The light powers the plane's propellers and charges the plane's batteries. At night, the Solar Impulse 2 runs on stored power.
Piccard says inventing other forms of energy is important. He said it must continue to improve lives "for clean technologies, for renewable energy."
Solar-powered air travel is not yet ready for passengers. It is too slow and there can be problems if weather is bad. Piccard thinks that someday all airplanes might be electric. It might be boring in the future. But for today, "it can never be boring," he said.
Piccard landed his plane in California on Saturday night. He flew for 62 hours, nonstop from Hawaii. He did not use any fuel.
Piccard and pilot Andre Borschberg take turns flying the Solar Impulse 2. They have been traveling around the world for more than a year. Last March, the plane took off from the United Arab Emirates, which is a country in the Middle East. The plane made stops in Asian countries including Myanmar, China and Japan.
It was risky to fly above the Pacific Ocean. There were not many places to land.
The pair have shown that it is possible "to fly many days, many nights, that the technology works," Borschberg said. He is 63 years old. He flew the plane on a five-day trip from Japan to Hawaii. He kept himself awake by doing yoga and meditation.
The Solar Impulse 2 proves that it is possible to fly for five days in a solar-powered plane. The pilots have faced a few bumps along the way, however.
First, the team was delayed in Asia. Then the plane did not make it from China to Hawaii on the first try. The crew had to reroute to Japan because of bad weather and a damaged wing.
A month later, with better weather conditions, the plane left Japan for Hawaii. However, it was forced to stay on the islands after the plane's battery system got heat damage on its flight from Japan.
The plane will make three more stops as it crosses the United States. Then it will fly across the Atlantic Ocean to Europe or northern Africa.
Borschberg said the plane will take off later this week. Its next stop is set to be Arizona, but that will depend on weather.