The pilot and designer of a private rocket plane say they are confident it could return to the sky next week in a quest to claim a multimillion-dollar prize, despite a harrowing flight in which the spacecraft rolled dramatically while hurtling toward the edge of the atmosphere.

As spectators and controllers nervously watched from the ground, SpaceShipOne (search) corkscrewed dozens of times Wednesday at nearly three times the speed of sound.

Test pilot Michael Melvill (search) ignored a warning to abort Wednesday's flight to complete the first stage of a quest to win a $10 million prize.

The problem was being analyzed by the spacecraft's builders, who must decide whether to proceed with another flight Monday, well ahead of the two-week deadline to qualify for the Ansari X Prize (search).

Melvill and spacecraft designer Burt Rutan (search) said Wednesday that were confident the Monday flight would go on. Rutan said rolling occurred during flight simulations, and it was not a complete surprise when it happened.

"We don't know exactly what went wrong. It's likely that it was something silly I did," Melvill told NBC's "Today" show on Thursday. "If I'd kicked a rudder pedal, for example, at that speed it would have induced that sort of a rudder roll that we saw. But we're looking at the data and we'll know more later."

Rutan said he asked Melvill to shut down the engine, but Melvill kept going until he reached the altitude specified under the rules for the X Prize, a bounty offered to the first privately built, manned rocket ship to fly in space twice in a span of two weeks.

"I did a victory roll at the top," the 62-year-old Melvill joked from atop the spaceship after it glided safely to a landing.

SpaceShipOne, with Melvill at the controls, made history in June when it became the first private, manned craft to reach space.

The Ansari X Prize will go to the first craft to safely complete two flights in a 14-day span to an altitude of 328,000 feet, or 62 miles — generally considered the point where the Earth's atmosphere ends and space begins.

The St. Louis-based X Prize Foundation is offering the bounty in hopes of inspiring an era of space tourism in which spaceflight is not just the domain of government agencies such as NASA.

Rutan, with more than $20 million from Microsoft billionaire Paul Allen (search), secretly developed SpaceShipOne — which has a wing span of just 16.4 feet — and is well ahead of two dozen teams building X Prize contenders around the world.

During its 81-minute flight, SpaceShipOne climbed to 337,500 feet — nearly 10,000 feet above its target, said Gregg Maryniak, executive director of the X Prize Foundation. The craft made more than two dozen unexpected rolls as the fat fuselage and spindly white wings shot skyward.

Rutan said controllers asked Melvill to shut the engine down early because of the rolling, but Melvill kept going until he was certain he would reach the target altitude.

"We actually were asking him to go ahead and abort, to shut it off to where he wouldn't have gone the (62 miles). He stayed in there just for a handful of seconds more," Rutan said.

Melvill said he did shut down the engine 11 seconds earlier than planned after determining the craft would reach its target.

The mission began when a specially designed jet with the ship under its belly took off from the desert north of Los Angeles. At 47,000 feet, SpaceShipOne was released, and Melvill fired its rocket motor and pointed the nose toward space.

A crowd of VIPs watched from below the airport control tower. The mission was televised live.

The Ansari X Prize was modeled on the $25,000 prize that Charles Lindbergh (search) won in his Spirit of St. Louis for the first solo New York-to-Paris flight across the Atlantic in 1927.

The X Foundation, the prize's sponsor, is supported by donors including Dennis Tito, an American who spent $20 million to fly in a Russian craft as the first space tourist, and Lindbergh's grandson Erik Lindbergh, a pilot.