NTSB changes position on spaceship crash US officials think a prematurely-deployed lever may have led to the crash of Virgin's SpaceShipTwo. INVESTIGATORS have given a precise timeline of the devastating Virgin Galactic spaceship crash, detailing exactly when a slowing mechanism was wrongly deployed, but said they could not determine who activated it. THE co-pilot of the SpaceshipTwo died in the crash on Friday over California's Mojave desert while the pilot survived the disaster, which has called into question Virgin chief Richard Branson's dream of tourist flights to the edge of space. Investigators said on Sunday 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 co-pilot Michael Alsbury. But at a final on-scene press briefing late on Monday, National Transportation Safety Board acting chairman Christopher Hart said he had been mistaken in identifying the co-pilot. Video showed the person in the right seat move the lock-unlock lever, but Hart said investigators do not yet know which of the two crew - Alsbury, or pilot Pete Siebold, who survived - moved it. Setting out the exact timeline, he said that the SpaceShipTwo was released from its mothership WhiteKnightTwo - which flew it up to some 45,000 feet - at 10.07 and 19 seconds. Two seconds later the engines started. Eight seconds after that, at 10.07 and 29 seconds, the rocket reached .94 Mach, accelerating to 1.02 Mach by 10.07 and 31 seconds. In that two-second period the lock-unlock lever was switched and the "feathering" mechanism started to deploy. At 10.07 and 34 seconds the data and video feeds from the rocket stopped, as it disintegrated over the desert. He reiterated that investigators would likely not announce a probable cause of the crash for up to 12 months. Branson said earlier on Monday that the deployment of the slowing mechanism may "well be" the cause of the catastrophe. Speaking on NBC's Today show Monday, Branson said he hadn't seen the cockpit video showing the co-pilot triggering the lock-unlock switch. Branson wants to ferry wealthy customers to the edge of space, charging $US250,000 ($A270,489) per ticket, and the crash is expected to delay the program. In an interview with CNN, Branson vowed to press ahead, once the cause of the crash was identified. If test pilots hadn't taken risks, we wouldn't have had the 747. Two blew up in early days of airline travel. Now airline travel is as safe as anything," he said. We've got to go through the difficult testing stage of creating a space line in order to make it safe for travellers who want to travel on that space line in the years ahead. We will persevere and will succeed. He also reiterated that he and his son will be on the first commercial flight. There is no way I would ask others to travel on Virgin Galactic unless I'd been the first to go myself. Therefore I will certainly be the first to travel," he said.