But the long-held view is the boundary is 62 miles. It's also the first time that a crewed vehicle built for commercial, passenger service, has reached space. As of this writing, NASA is unable to send astronauts on its own to sub-orbit let alone to orbit.
It surpassed the height the US Air Force considers the boundary of space (80km), and marks the first manned flight to space from US soil since 2011. Aboard were test pilots Mark "Forger" Stucky and C.J Sturckow.
The VSS Unity reached a top speed of over 1,530 miles per hour, or beyond Mach 2.
Soon, the vehicle pointed nearly straight up, as it streaked through the same skies over the California desert where Chuck Yeager first broke the sound barrier in 1947.
The rocket ship hit an altitude of 51 miles (82 kilometers) before beginning its gliding descent, said mission official Enrico Palermo. Virgin Group founder Richard Branson was on hand to watch the historic moment. "It was maybe tears of relief as well".
For comparison, astronauts at the orbiting International Space Station fly some 250 miles (400 km) above Earth.
Branson said "ultimately" he would like to see the price fall to around £30,000 ($40,000) or £38,000 ($50,000) over the next ten years.
The aircraft reached an altitude of 271,268ft as it made its rapid ascent into space. But that may soon change.
December 13's flight was at a higher altitude then the previous flights earlier this year of 16.0 miles, 21.7 miles, and 32.3 miles flown in April, May, and July respectively. We started Virgin almost 50 years ago dreaming big and loving a challenge, Branson said via a company-issued release.
Virgin Galactic's development of its commercial spaceline has taken longer than expected.
Then, in 2014, SpaceShipTwo broke apart during a test flight by Scaled Composites when the co-pilot prematurely unlocked the "feathering" system and it began to deploy.
As federal investigators investigated the crash, Branson pondered whether to continue, ultimately vowing to press on.
More than 600 people from 50 countries have reserved places to fly with Virgin Galactic when all testing has been completed.
Branson said he has invested almost $1 billion of his own money into the venture.
"Space is not cheap", he said. "How on Earth do I describe the feeling?" he said.
"The amusing thing about races is people always say, "We're not in a race" until they actually win", Branson said.
"If all goes to plan our pilots will experience an extended period of micro-gravity as VSS Unity coasts to apogee", Virgin Galactic said.
Space enthusiasts are anxiously awaiting another test of a rocket-powered supersonic spacecraft, which could open the door even wider to the possibility of space tourism in the near future.