Unity took off from the Mojave test centre in California and climbed 51 miles (82km) before beginning its descent early on Thursday.
Once the mothership Eve reached an altitude of about 13,110 metres (43,000 feet), it released the space plane VSS Unity in the sky.
"We will now push on with the remaining portion of our flight test programme, which will see the rocket motor burn for longer and VSS Unity fly still faster and higher".
Regardless of whether SS2 reached "space" today, the flight marks an achievement that has been more than a decade in the making and moves Richard Branson's company one step closer to flying passengers on suborbital flights. (That's the subject of some debate, with others arguing the boundary ought to lie at 62 miles, or 100 km.) But no matter how you parse it, the view was tremendous. In October 2014, its spacecraft crashed during a test flight over the Mojave Desert, killing one of the pilots aboard and severely injuring the other. After reaching an altitude above 40,000 feet, Unity was released and the crew used a 60-second burn to push the spacecraft to a speed of Mach 2.9, almost three times the speed of sound.
Flown by two pilots, Mark Stucky and Nasa astronaut Frederick Sturckow, the flight is also the first time that humans has been sent into space from USA soil since Nasa's space shuttle programme ended in 2011. Virgin celebrated the vessel's first encounter with space, but the company is using the loosest definition of "space". The astronaut designation is in keeping with US military and NASA pilots who when they fly above 80 kilometers are reclassified as astronauts.
The development also likely comes as welcome news to the prospective space tourists who have already invested heavily in tickets aboard the first official flights, whenever they get off the ground. Pilots Mark "Forger" Stucky and Frederick "CJ" Sturckow were carried aloft in Virgin Space Ship (VSS) Unity by the WhiteKnightTwo aircraft. The flight on December 13 was Virgin Galactic's longest rocket-powered flight ever.
Thursday's launch was also a major milestone for a growing commercial space industry, which for all its triumphs has yet to show it can routinely fly humans into space. "Space is not cheap", he said.
The United States has not been able to launch anyone into space since it terminated the space shuttle program. At a cost of $250,000 for a 90-minute flight, seats do not come cheap for this ultimate thrill ride that will take you out-of-this-world (depending on where you believe the boundary to be). Virgin's researchers are, however, favouring the lower figure as a more accurate representation. The crew capsule reached 93 kilometers altitude, however NASA's statement was that it counts it as a spaceflight for Hague and his Russian crew mate Aleksey Ovchinin because they "launched and landed in a spacecraft or an intended mission to the International Space Station" without mentioning any altitude.