While it might seem that photovoltaic cells—which generate electricity from sunlight—might not be all that useful on a cloudy day, consider their usefulness at night. And consider being at 28,000 ft on an airplane powered by photovoltaics in the middle of the night. On July 7, 2010, a prototype plane from Switzerland-based Solar Impulse piloted by Betrand Piccard, the HB-SIA, flew for 26 hours and nine minutes, making it the first solar airplane to harness enough of the sun’s energy to power it through an entire night.

What’s more, Solar Impulse says it still had plenty of battery power left when it landed. (We’re guessing that Piccard was probably running on empty, however.)

Equipped with 12,000 solar cells on its 193-ft wingspan, the HB-SIA collects the sun’s energy and stores it as electricity in lithium ion batteries. The batteries power the plane’s four electric motors. The plane had a top speed of 70 mph, but an average flight speed of only 26 mph. At that rate it would take about 115 hours of flying time from New York City to Los Angeles.

But Solar Impulse isn’t stopping with the HB-SIA. The company says it wants to develop a second-generation prototype to fly across the Atlantic Ocean. Then, it wants to fly around the world. Here’s hoping that the average speed is increased by then, because otherwise it would take on the order of 38 days for the circumnavigation.