The chief executive of the space tourism company Virgin Galactic says the company will carry on with its plans to take paying customers to the edge of space despite the recent accident involving its SpaceShipTwo vehicle.

Virgin Galactic CEO George Whitesides called the day two weeks ago when SpaceShipTwo broke apart during a test flight and killed one of its two pilots "a tragic day," but said the company would continue with the venture backed by British entrepreneur Richard Branson.

"We have a new spaceship that's going to be ready in a few months," he said in a statement released by the company. "So we're going to make sure we get that one as safe as we can and keep going."

Investigators from the National Transportation Board, looking at the wreckage of SpaceShipTwo that was scattered across California's Mojave Desert, have been focusing on an apparent action by co-pilot Michael Alsbury to prematurely unlock the rocket plane's movable tail.

The tail is not intended to move until the re-entry part of the craft's flight, to properly orient it as it begins a descent through the atmosphere.

A final report on the crash and its cause could take up to a year to prepare, the NTSB said.

Alsbury was killed in the crash, while pilot Peter Siebold was hurled from the disintegrating craft still attached to his seat.

He managed to separate himself from the seat and his parachute automatically deployed, although injuries he sustained kept him in a hospital for three days.

"There's a reason why test pilots are respected as some of the most brave members of our society," Whitesides said some time before the fatal test flight. "They are putting themselves in harm's way to make vehicles better for the rest of us, safer for the rest of us."

The crash was seen by many as a significant setback in Virgin Galactic's plan to offer rides to space for passengers willing to pay $250,000 for a ticket, a program that has already experienced years of delay.

SpaceShipTwo had made dozens of flights, although most of them were unpowered gliding flights after release from its WhiteKnightTwo mother ship.

The fatal flight was just the fourth in which the craft had fired its engines, and the first using a new rocket fuel developed to give the engine additional thrust.

The company would learn from the tragedy and work to ensure nothing like it would happen again, Whitesides said.

"We make sure the engineers are in charge and that's what we've done from day one," he said. "The fact that the program has taken longer is a sign we are listening to the engineers."

"While this has been a tragic setback, we are moving forward and will do so deliberately and with determination."