Virgin Galactic has flown its new space plane freely for the first time, two years on from the fateful crash that killed pilot Michael Alsbury.

The unpowered flight of VSS Unity took place on Saturday December 3 in the Mojave Desert, with it gliding through the air after being detached from its “mothership” carrier aircraft, WhiteKnightTwo (or VMS Eve). This was the fifth flight for Unity, but the first time it had flown alone. Its first flight, in so-called "captive carry", was back in September.

The entire flight lasted 1 hour and 20 minutes, with Unity in free flight for 10 minutes, piloted by Mark Stucky and Dave Mackay. Unity descended from an altitude of 15 kilometers (9.5 miles) where it was released, reaching a maximum speed of 740 kilometers per hour (460 miles per hour), before landing at the Mojave Air and Space Port.

Ultimately, Richard Branson's Virgin Galactic is preparing for powered flights of Unity, when it will use its rocket motor to propel itself, before actually venturing into suborbital space (beyond an altitude of 100 kilometers). The company said there would be up to 15 glide test flights before that happened, though, and firm dates have not yet been set.

Of course, the final goal for the eight-seater vehicle (two pilots, six passengers) is to start taking paying customers on short 6-minute hops into space at $250,000 a ticket. Currently, more than 600 people have signed up for a ride.

Unity’s predecessor, VSS Enterprise, was destroyed in October 2014. An investigation found the cause was a premature unlocking of the vehicle’s “feathering” system, where the tail can be moved to help the vehicle re-enter the atmosphere. The vehicle instantly broke apart, killing Michael Alsbury. His co-pilot, Peter Siebold, miraculously survived.

So it’s understandable that Virgin Galactic and the vehicle’s developer, Scaled Composites, want to make sure everything is working properly this time around. That means, though, it may be years before we see Virgin Galactic begin actual space tourism flights.