SpaceShipOne, designed by pioneer engineer Burt Rutan and paid for by Microsoft co-founder Paul Allen, went to an altitude of just over 100 kilometers (62 miles), said Rutan's company, which admitted problems had prevented the craft reaching its target altitude.

The craft returned safely to Earth after about 90 minutes to be acclaimed by Rutan, Allen and about 10,000 thousand people at Mojave airport in the California desert.

"It was a mindblowing experience," said Mike Melvill, the 62-year-old South African-born pilot who was at the controls of SpaceShipOne for the historic flight.

"You have got a hell of a view from 62 miles," he added.

The rocket-plane was launched from a specially made jet, named White Knight, at an altitude of 15 kilometers (48,000 feet). Its engine ignited for three minutes, powering SpaceShipOne into the fringes of space before it fell back to Earth, the mission control said.

Rutan said SpaceShipOne had reached 328,491 feet (100.12 kilometers), farther than any other privately financed mission into space.

Melvill gradually took control of the craft again and from 25 kilometers (80,000 feet) altitude, it glided for about 17 minutes back to the landing.

Rutan admitted a steering problem had forced organisers to cut back the mission.

"We did get there -- 328,491 feet," Rutan said. "We were going to go to 360 but these anomalies meant that we barely got over."

The problem was in the flight controls. "It was no big deal in terms of safety but it was not a smooth flight in terms of trajectory," he added.

"The anomaly we had today is the most serious flight safety systems problem that we have had in the entire program and the fact that our backup system worked and we made a beautiful landing makes me feel very good. The backup sytems worked."

Rutan, 61, set up his company, Scaled Composites, to develop and build SpaceShipOne, which cost 20 million dollars.

After his landing, Melvill, a vice president of the company, paid tribute to Rutan's expertise.

"This could not have been done without the brilliant brain that this guy has," he said.

"He thought it out, he thought of everything to make it work and it worked exactly as he thought, even though we argued with him and threw up roadblocks."

Rutan also developed Voyager, the aircraft which in 1986 became the first to go around the world without refueling.

Rutan said some "risks" had been taken in the design of SpaceShipOne -- a winged, white rocket plane that weighs about three tonnes -- but most of it was the same as his first conception in 1999.

At 15 kilometers (48,000 feet), the liquid and solid fuel engine propelled SpaceShipOne upwards at a speed of about 3,500 kilometers (2,200 miles) per hour to a height of some 50 kilometers (160,000 feet) above the planet.

When the rocket's fuel had been spent, SpaceShipOne kept going up for about three minutes.

Rutan and Allen are aiming to bring space flight within the range of the general public as well as win a prize for the first private mission beyond Earth's atmosphere.

"The flight is a milestone that may lead to a new space age," Rutan said Sunday. "There is an enormous hunger to fly in space and not just to dream about it.

"The new private space entrepreneurs have a vision. We do want our children to go to other planets."

Sean O'Keefe, chief administrator of the US National Aeronautics and Space Administration, which has dominated space exploration for the past 40 years, paid tribute to the newcomers.

"They are doing much to open the door to a new marketplace offering the experience of weightlessness and suborbital space flight to the public. We applaud the remarkable achievement of Burt Rutan, Paul Allen and test pilot Mike Melvill."

Rutan is also eyeing a 10-million-dollar prize for the first privately funded space vehicle that can carry two passengers and a pilot to an altitude of 100 kilometers (62.5 miles) twice in two weeks.

The Ansari X Prize has been offered by the X Prize Foundation, a US-based group, in a bid to encourage commercial space travel. About 25 teams from seven countries are said to be in contention.

SPACE.WIRE