A solar-powered plane nearing the close of a cross-continental journey landed at Dulles International Airport outside the nation's capital early Sunday, only one short leg to New York remaining on a voyage that opened in May 2013.
Solar Impulse's website said the aircraft with its massive wings and thousands of photovoltaic cells "gracefully touched down" at 12:15 a.m. EDT after 14 hours and four minutes of flight from Cincinnati, Ohio, to Dulles in Washington's Virginia suburbs.
Pilot Bertrand Piccard was at the controls for the last time on the multi-leg "Across America" journey that began May 3 in San Francisco. His fellow Swiss pilot, Andre Borschberg, is expected to fly the last leg from Washington to New York City's John F. Kennedy International Airport in early July, the web site added.
It is the first bid by a solar plane capable of being airborne day and night without fuel to fly across the US, at speeds reaching about 40 mph. The plane opened by flying from San Francisco via Arizona, Texas, Missouri and Ohio onward to Dulles with stops of several days in cities along the way.
Organizers said in a blog post early Sunday that Piccard soared across the Appalachian mountains on a 435-mile (700-kilometer) course from Cincinnati to the Washington area, averaging 31 mph (50 kph). It was the second phase of a leg that began in St. Louis.
The plane, considered the world's most advanced sun-powered aircraft, is powered by about 12,000 photovoltaic cells that cover its enormous wings and charge its batteries during the day. The single-seat Solar Impulse flies around 40 mph and can't go through clouds; weighing about as much as a car, the aircraft also took longer than a car to complete the journey from Ohio to the East Coast.
Despite its vulnerabilities to bad weather, Piccard said in a statement that the conclusion of all but the final leg showed that sun-powered cross-continent travel "proves the reliability and potential of clean technologies."
Organizers said fog at Cincinnati Municipal Lunken Airport was a concern that required the ground crew's attention before takeoff just after 10 a.m. Saturday. The crew gave the plane a gentle wipe-down with cloths because of condensation that had formed on the wings.
"The solar airplane was in great shape despite the quasi-shower it experienced" before takeoff from Cincinnati, the web site added.
Washington was the first East Coast stop before the final planned leg to New York.
Organizers said the flight into the nation's capital was an emotional one for Piccard as it was his last on the cross-country flight before Borschberg has the controls on the final trek to New York.
At each stop along the way, the plane has stayed several days, wowing visitors. Organizers said a public viewing of the aircraft would be held Sunday afternoon at Dulles.
As the plane's creators, Piccard and Borschberg, have said their trip taking turns flying the aircraft solo was the first attempt by a solar airplane capable of flying day and night without fuel to fly across America. They also called it another aviation milestone in hopes that the journey would whet greater interest in clean technologies and renewable energy.
The Swiss pilots said in a statement that they expected to participate in an energy roundtable and news conference Monday with US Energy Secretary Ernest Moniz about the technology. They have said the project's ultimate goal is to fly a sun-powered aircraft around the world with a second-generation plane now in development.
Borschberg also said in a statement Sunday that the pilots are eyeing 2015 for a worldwide attempt, adding their 'Across America' voyage had taught them much as they prepare.