Virgin Galactic conducted another successful drop test of its SpaceShipTwo suborbital spacecraft Jan. 13, the latest in a series of smooth solo glides over the California desert for the commercial spaceship.

SpaceShipTwo, designed and built by Mojave, Calif.-based Scaled Composites, was released from its WhiteKnightTwo mothership a little after 8 a.m. local time Jan. 13 and returned in glide mode to a runway at the Mojave Air and Space Port. The high-altitude flight did not reach space, but was the fourth in a series of demonstration flights ahead of an actual suborbital spaceflight test.

โ€œWe had another great flight today, piloted by Mark Stucky and co-pilot Clint Nichols, a good start for what will be a busy year of flight tests,โ€ said George Whitesides, Virgin Galacticโ€™s chief executive officer.

The suborbital spaceliner is designed to carry six passengers and two pilots, flying to the edge of space for a spectacular view of the Earth and several minutes of weightlessness.

SpaceShipTwo conducted its first manned gliding test flight Oct. 10, followed by a second Oct. 28 and a third Nov. 17.