Virgin Galactic's SpaceShipTwo Glides Through a Dry Run

Virgin Galactic's SpaceShipTwo rocket plane was set loose on Thursday over California's Mojave Desert for a gliding test flight — and although its hybrid rocket motor wasn't lit up, the pilots checked out the propulsion system's plumbing for a future blast.

The plane was tucked beneath its WhiteKnightTwo mothership for the morning takeoff from the Mojave Air and Space Port, and when the paired aircraft reached the proper altitude, SpaceShipTwo was released for a "cold flow" test. A series of@VirginGalactic tweets tracked the test's progress:

Virgin Galactic's SpaceShipTwo rocket plane comes in for a landing after a gliding test at the Mojave Air and Space Port in California on Thursday.

SpaceShipTwo's last rocket-powered test took place back in January. Since then, Virgin Galactic and its partners at Scaled Composites and Sierra Nevada Corp. have switched to a different kind of plastic-based fuel. Once everything checks out, powered tests are to resume with the eventual aim of sending SS2 into space.

Virgin Galactic's billionaire founder, Richard Branson, could take a ride as early as this year, with commercial service beginning soon afterward. More than 700 people have paid as much as $250,000 each for suborbital space tours.