If successful, it would be a major step toward the long-delayed dream of commercial space tourism.
The next test flight could come as early as Thursday with the rocket-powered spacecraft soaring high above California's Mojave Desert.
Development of the Virgin Galactic spaceship took far longer than expected and endured a setback when the first one broke apart during a 2014 test flight, killing the co-pilot.
A company statement says the next test flights aim to "reach a space altitude for the first time."
Hundreds of people have signed up to pay as much as $250,000 for a supersonic thrill ride on the six-passenger spaceship.