Virgin Galactic has taken one small step closer into space, after it was granted a license for experimental rocket tests in the United States.
Scaled Composites, which is Virgin's design partner, was granted the one-year licence by the Federal Aviation Administration (FAA).
The development will lead to the companies testing rocket motors on its SpaceShipTwo craft, which is launched from a twin-fuselage plane.
The ship has already undergone glide testing, completing 16 flights.
Six passengers will eventually be able to ride SpaceShipTwo on a sub-orbital flight - and 500 people including celebrities and wealthy investors have already signed up, paying tens of thousands of dollars for the privilege.
Its predecessor, SpaceShipOne, won the $10m Ansari X Prize in 2004 for the first private human space flight, after three suborbital journeys up to 70 miles above the Earth.
According to Scaled Composite president George Whitesides the granting of the FAA permit is a "a major step closer to bringing our customers to space".
Virgin Galactic said:
With this permit now in hand, Scaled is now authorised to press onward towards rocket-powered test flights. In preparation for those powered flights, SpaceShipTwo will soon return to flight, testing the aerodynamic performance of the spacecraft with the full weight of the rocket motor system on board.
Integration of key rocket motor components, already begun during a now-concluding period of downtime for routine maintenance, will continue into the autumn.
Scaled expects to begin rocket powered, supersonic flights under the just-issued experimental permit toward the end of the year.