But the long-held view is the boundary is 62 miles.
They too are hoping to take their first commercial passengers in 2019. NASA and the U.S. define anyone who flies at this altitude as an astronaut.
Virgin Galactic considers that altitude to be the threshold of space because it's defined that way by the Air Force and other USA agencies, although others have long considered the boundary to be higher.
The mission was piloted by Mark "Forger" Stucky and C.J Sturckow (as noted on NASASpaceFlight, Sturckow is no stranger to space having traveled there four times on board NASA's retired fleet of shuttles).
Virgin Space Ship Unity was released from a carrier aircraft and ignited its rocket engine.
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. Sir Richard Branson's company launched a spacecraft more than 50 miles into the air Thursday, not reaching orbit but successfully meeting the Federal Aviation Administration's definition of space, the Washington Post reports.
"We should be in space within weeks, not months", the Virgin Group founder and CEO told CNBC. Branson, wearing a leather bomber jacket, hugged his son as the spacecraft raced upwards and a commentator called out the altitude.
That debate about whether the vehicle reaches space on this test flight, though, assumes that the flight will go well. "Had plenty of time to look around".
An artist’s impression of the Virgin SpaceShipTwo
The Kármán line, at 100km, has commonly been regarded as where space starts, but Virgin Galactic will point to discussions within the scientific community about revising this figure downwards to 80km. Branson plans to be the first passenger aboard VSS Unity.
The endeavor began in 2004 when Branson announced the founding of Virgin Galactic in the heady days after the flights of SpaceShipOne, the first privately financed manned spacecraft that made three flights into space. But that may soon change.
Commerciaaeroplaneses typically fly at an altitude of about six miles.
"Safety's all that matters if you're putting people into space", he said.
But a series of delays has grounded the firm, which suffered a disaster four years ago, when the VSS Enterprise broke apart in midair, killing co-pilot Michael Alsbury and seriously injuring pilot Peter Siebold.
The VSS Unity arrives safely back on the ground after achieving a test flight milestone. "We've got to make this a profitable venture and I think we can make it a profitable venture". "Space is not cheap", he said. Branson has said he intends to be on the first commercial flight. A special "feather" system is then used for reentry, wherein the craft folds its wings and behaves like a traditional space capsule until the air thickens again, at which time the wings unfold again and behave like a space plane, gliding back to Earth and landing on a landing strip.
"Overall the goal of this flight is to fly higher and faster than previous flights", said a statement from Virgin Galactic.
Eventually, the company would like to turn those spaceports into "future hubs for a network of intercontinental transportation nodes" where the spaceships can transport people across the globe in a matter of hours. "I think we can authentically say that we're obviously hoping for a good day tomorrow but the risk of a not good day is still possible".