ONE pilot has been killed and another seriously injured after a suborbital passenger spaceship being developed by Sir Richard Branson's Virgin Galactic company exploded during a test flight.

The accident, at the Mojave Desert in California, happened shortly after the rocket, called SpaceShipTwo, separated from the jet aircraft that carried it aloft for its high-altitude launch, according to the Federal Aviation Administration. The identities of the pilots involved were not released last night. They are understood to have been employed by Virgin Galactic's partner business Scaled Composites, which designed and built the spacecraft.

The National Transportation Safety Board said it was sending one of its "go-teams" to investigate the accident and Sir Richard said he was flying to California immediately.

George Whitesides, chief executive of Virgin Galactic, said: "Space is hard, and today was a tough day."