PAYERNE, Switzerland (AP) -- Swiss adventurer Bertrand Piccard's team took its round-the-world solar plane prototype into the skies for the first time Wednesday, with four propellers lifting the massive craft off the ground at near bicycle speed.
Piccard said the two-hour test flight will examine if the plane, with the wingspan of a Boeing 747 and the weight of a small car, can keep a straight trajectory. The team plans to fly it around the world next year.
"To fly without fuel, we have to make it fly in line," said Piccard, who in 1999 copiloted the first nonstop round-the-globe balloon flight. "There might be things that go wrong - maybe a technical problem, engine failure or a part breakdown."
The takeoff appeared smooth, however.
At a military airport in the Swiss countryside, the "Solar Impulse" plane lifted off after only a short acceleration on the runway, reaching a speed no faster than 45 kph (28 mph). It slowly gained altitude above the green and beige fields, and disappeared eventually into the horizon as villagers watched from the nearest hills.
The weather for the maiden flight was sunny.
The euro70 million project has been conducting flea-hop tests since December, taking the plane no higher than 60 centimeters (2 feet) in altitude and 300 meters (1,000 feet) in distance. A night flight is planned later this year, and then a new plane will be built based on the results of those tests.
The big takeoff is planned for 2012, and it will use not an ounce of fuel.
Using almost 12,000 solar cells, rechargeable lithium batteries and four electric motors, Piccard and co-pilot Andre Borschberg plan to take the plane around the world with stops to allow them to switch over and stretch after long periods in the cramped cockpit.
The circumnavigation will take time.
With the engines providing only 40 horsepower, the plane will fly almost like a scooter in the sky, at an average flight speed of 70 kph (44 mph). The trip will be split up into five stages - keeping the plane in the air for up to five days at a time - with the stopovers also allowing the team to show off their creation.
Solar flight isn't new but Piccard's project is the most ambitious.
In 1980, the fragile Gossamer Penguin ultra-lightweight experimental solar plane flew short demonstration flights with one pilot on board. A more robust project called the Solar Challenger flew one pilot from France to England in a five-hour-plus trip in 1981.
Solar plane technology recalls the early days of manned flight, and the slow ascent of the Solar Impulse was somewhat reminiscent of the Wright brothers pioneering experiments over a century ago.
"It's a very important moment" after seven years of work, said Borschberg.
Test pilot Markus Scherdel manned the flight, which wasn't supposed to surpass 1,000 meters (3,280 feet) in altitude.
Below waited numerous people involved with the project and Piccard, who comes from a long line of adventurers. His late father Jacques plunged deeper beneath the ocean than any other man, and grandfather Auguste was the first man to take a balloon into the stratosphere.