Investigators have pointed out that a lock-unlock lever, used to activate a process in SpaceShipTwo's tail section typically to slow it for re-entry into the Earth's atmosphere had been moved by the co-pilot.

A short time later a so-called "feathering" process in which the tail section rotates to increase drag on the spacecraft was deployed, at which point the pioneering vessel began to disintegrate.

It was unclear if the "feathering" which acts like a badminton shuttlecock's feathers, slowing the aircraft down during re-entry and pointing it in the right direction started on its own or as a result of the lever being moved.

Investigators from the National Transportation Safety Board (NTSB) have emphasised the cause of Friday's accident in the Mojave Desert has not been established.

Branson, speaking on NBC's Today show yesterday, said he hadn't seen the cockpit video showing the co-pilot triggering the lock-unlock switch.

"The NTSB, you know, are leading the investigation. And we go by exactly what they tell us," he said.

"But, you know, if the deployment did take place early, obviously, they're indicating that may well be the cause. But we need them to examine that further and let us know," he added.

But Branson also hit out against "hurtful" critics and "self-proclaimed experts" after a rocket scientist said the company had ignored safety warnings ahead of the deadly crash of one of its spacecraft.

"I've never seen such irresponsible innuendo and damaging innuendo," the British business tycoon told Britain's Sky News television, referring to critical press reports in Britain.

"The fuel tanks and the engine were intact, showing there was no explosion, despite a lot of self-proclaimed experts saying that was the cause," he said.

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