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.

“We 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,” said George Whitesides, Virgin Galactic’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.