SpaceShipOne is scheduled to take off at around 7:00 am (1400 GMT) and blast out of the earth's atmosphere just over an hour later in its quest for the Ansari X Prize purse, aimed at spurring a new era of commercial space travel.

Organisers of the so-far unique venture also confirmed Friday that the groundbreaking rocketship's pilot Mike Melvill successfully took the craft to 337,500 feet, or 103 kilometers (64 miles), on Wednesday's first flight.

In order to win the prize, funded by a private organisation and aimed at mimicking the 1920s-era Orteig prize that aviator Charles Lindberg won when he crossed the Atlantic in 1927 and which kickstarted the age of commercial air travel, the craft had to break through the 328,000 foot barrier.

In addition, space vehicles vying for the prize must send a manned, reusable spacecraft into space twice within two weeks, carrying the pilot and the equivalent weight of two passengers.

There are 26 vehicles in contention for the Ansari prize, but SpaceShipOne, designed by pioneer aviator Burt Rutan, is far ahead of the others and is by far the favourite to win the prize.

Designer Rutan said after Wednesday's dramatic flight that he and his team would examine flight data carefully to establish what caused the craft to corkscrew through the air dozens of times before it entered space to make sure there was no problem with the ship.

Veteran South African test pilot Melvill conceded that the hair-raising incident might have been his fault and that he "must have stamped on something" he should not have as the rocket plane was flying at speeds of around 3,000 kilometers an hour.

Like the last two SpaceShipOne sub-orbital flights, Monday's attempt to snatch the X Prize will take place at Mojave airport in the middle of the California desert.

The name of the pilot for the next flight has not yet been announced, but Melvill, who in June became the world's first commercial astronaut when he took the craft into space for the first time, said it would not be him.

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