Virgin Galactic chief executive George Whitesides said his company will soon return to powered flights for the first time in three years.

"We're ready to go into powered flight," Whitesides said on Thursday at the Mars Society Convention in Irvine, California.

Virgin Galactic has not tested a powered flight of one of its spaceships since the fatal crash of Spaceship Enterprise on Oct. 31, 2014. An investigation by the National Transportation Safety Board found the pilot prematurely unlocked the spaceship's "feather system," causing the vehicle to break apart during rocket-powered flight.

Engine testing for the spaceship company's new vehicle, Spaceship Unity, is complete, and "a very small number of glide flights" remain before Virgin Galactic returns to powered flight, Whitesides said.

Virgin Galactic's subsidiary The Spaceship Company is also building two more spaceships, the hulls of which were visible in a photo Whitesides showed of the company's manufacturing facility.