The incident described as minor occurred Thursday on a runway at the Mojave Air and Space Port.
Aircraft builder Scaled Composites says in a statement that there was a mechanical problem with the left landing gear of the WhiteKnightTwo, a four-engine jet that will serve as the mothership to Virgin's passenger-carrying spaceship.
The company did not describe the problem in any detail but says there were no injuries and its spaceship was not attached to the jet at the time.
WhiteKnightTwo is designed to carry Virgin's spaceship to high altitude and then release the rocket, which will then fire its engine for a brief dash into space.
