Alone in the single-seat cockpit and high above the American Southwest, pilot Bertrand Piccard could hear only his plane's gear box and the quiet whine of four electric motors. No noisy jet engines.
He's flying Solar Impulse, considered the world's most advanced sun-powered plane.
Swiss pilots and co-founders of the project, Bertrand Piccard and Andre Borschberg, will take turns flying the plane, built with a single-seat cockpit. Piccard was at the controls for the first flight to Arizona.
Piccard piloted the craft cruising along the California coast after taking off from Moffett Field in Mountain View near San Francisco just after dawn on Friday. He passed over Edwards Air Force Base, where other aviation milestones have been made, and then touched down early Saturday morning at Phoenix Sky Harbor Airport. Solar plane takes off on cross-country US trip
He landed having used only three-quarters of the plane's battery power.
The plane, dubbed as Solar Impulse, took 18 hours and 18 minutes to reach Phoenix being a slow-speed flight. It completed the first of five legs with planned stops in Dallas, St. Louis and Washington on the way to a final stop in New York. Each flight leg will take about 19 to 25 hours, with 10-day stops in each city.
"It's a little bit like being in a dream," Piccard said as he stepped on the tarmac.
The plane's creators said the trip is the first attempt by a solar airplane capable of flying day and night without fuel to fly across America.
But Piccard said on Saturday afternoon that even more important than marking another aviation milestone is the hope that the journey will provide an exponential boost for interest in renewable energy and clean technologies; the plane has a wingspan of a jumbo jet, which allows the plane to conserve energy.
"If an airplane can fly day or night with no fuel, just on the sun's power, of course it means that everybody in daily life can use this technology for his house, for heating and cooling systems, for lighting, for cars, for trucks. There's so much we can do now to have a cleaner future," Piccard said.
This is a test model for a more advanced aircraft the team plans to build to circumnavigate the globe in 2015. It made its first intercontinental flight, from Spain to Morocco, last June.
Borschberg is hoping to pilot the last leg, which could afford him the chance to fly past the Statue of Liberty.
The plane, which has previously impressed audiences in Europe, is powered by about 12,000 photovoltaic cells that cover massive wings and charge its batteries.
The delicate, single-seat Solar Impulse can climb to 28,000 feet or so during the day to collect solar energy and charge the batteries. It flies at an average of 43 miles per hour (69 km per hour). It's wingspan and weight - which is as much as a car - makes it vulnerable to bad weather. It cannot fly in strong wind, fog, rain or clouds.
Its average speed for the first leg of the trip was about 60 knots with a tail wind, Borschberg said.
The project began in 2003 with a 10-year budget of 90 million euros ($112 million) and has involved engineers from Swiss escalator maker Schindler and research aid from Belgian chemicals group Solvay.
Borschberg and Piccard were ready for a series of tours over the next few days to show off the technology to Phoenix school children, university researchers and others.
"There are a lot of people who want to see this airplane," Piccard said.
Despite the aviation advancements made over the last century, Piccard said he and Borschberg have a lot in common with the early pioneers.
"One hundred years ago, the planes had to fly in good weather and there was only one person on board," Piccard said. "Now we have completely new technology, we fly with no fuel at all. But, of course, we need to fly in good weather and we carry only one pilot on board.
"We're starting a new cycle. It's really the beginning of something new."
(With inputs from AP and Reuters)