A working staff introduces the "Solar Impulse" at the Moffett Federal Airfield, Mountain View, California, April 20, 2013. The Swiss-made world's biggest solar-powered aircraft that doesn't use a single drop of fuel will begin traveling across the United States in early May. It'll take off on May 1 from the San Francisco Bay area and reach New York's JFK airport, the final destination, in early July. (Xinhua/Chen Gang)

"Solar Impulse" is seen at the Moffett Federal Airfield, Mountain View, California, April 20, 2013. The Swiss-made world's biggest solar-powered aircraft that doesn't use a single drop of fuel will begin traveling across the United States in early May. It'll take off on May 1 from the San Francisco Bay area and reach New York's JFK airport, the final destination, in early July. (Xinhua/Chen Gang)

Working staff prepare to push "Solar Impulse" indoor at the Moffett Federal Airfield, Mountain View, California, April 20, 2013. The Swiss-made world's biggest solar-powered aircraft that doesn't use a single drop of fuel will begin traveling across the United States in early May. It'll take off on May 1 from the San Francisco Bay area and reach New York's JFK airport, the final destination, in early July. (Xinhua/Chen Gang)

A working staff introduces the solar powered cells of "Solar Impulse" at the Moffett Federal Airfield, Mountain View, California, April 20, 2013. The Swiss-made world's biggest solar-powered aircraft that doesn't use a single drop of fuel will begin traveling across the United States in early May. It'll take off on May 1 from the San Francisco Bay area and reach New York's JFK airport, the final destination, in early July. (Xinhua/Chen Gang)

A mechanical worker examines "Solar Impulse" at the Moffett Federal Airfield, Mountain View, California, April 20, 2013. The Swiss-made world's biggest solar-powered aircraft that doesn't use a single drop of fuel will begin traveling across the United States in early May. It'll take off on May 1 from the San Francisco Bay area and reach New York's JFK airport, the final destination, in early July. (Xinhua/Chen Gang)

"Solar Impulse" is put indoor at the Moffett Federal Airfield, Mountain View, California, April 20, 2013. The Swiss-made world's biggest solar-powered aircraft that doesn't use a single drop of fuel will begin traveling across the United States in early May. It'll take off on May 1 from the San Francisco Bay area and reach New York's JFK airport, the final destination, in early July. (Xinhua/Chen Gang)

A mechanical worker supports the engine of "Solar Impulse" at the Moffett Federal Airfield, Mountain View, California, April 20, 2013. The Swiss-made world's biggest solar-powered aircraft that doesn't use a single drop of fuel will begin traveling across the United States in early May. It'll take off on May 1 from the San Francisco Bay area and reach New York's JFK airport, the final destination, in early July. (Xinhua/Chen Gang)

A working staff introduces the materials made up of "Solar Impulse" at the Moffett Federal Airfield, Mountain View, California, April 20, 2013. The Swiss-made world's biggest solar-powered aircraft that doesn't use a single drop of fuel will begin traveling across the United States in early May. It'll take off on May 1 from the San Francisco Bay area and reach New York's JFK airport, the final destination, in early July. (Xinhua/Chen Gang)

Kids view an introductory poster for "Solar Impulse" at the Moffett Federal Airfield, Mountain View, California, April 20, 2013. The Swiss-made world's biggest solar-powered aircraft that doesn't use a single drop of fuel will begin traveling across the United States in early May. It'll take off on May 1 from the San Francisco Bay area and reach New York's JFK airport, the final destination, in early July. (Xinhua/Chen Gang)