Solar plane on course for space after test flight

Swiss adventurer Bertrand Piccard, said the two-hour test was to see if the plane, with the wingspan of a Boeing 747 and the weight of a small car, can keep a straight trajectory.

"To fly without fuel, we have to make it fly in line," said Mr Piccard, who in 1999 co-piloted the first non-stop round-the-globe balloon flight. "There might be things that go wrong – maybe a technical problem."

At a military airport, the Solar Impulse plane lifted off after only a short acceleration, reaching a speed no faster than 28mph. It slowly gained altitude above the fields and disappeared eventually into the horizon.

The 70m project has been conducting flea-hop tests since December, taking the plane no higher than two feet and 1,000ft in distance.