The 'feathering' system on Virgin Galactic's SpaceShipTwo may have been deployed without command, prompting the fatal crash that tok place on Friday. The system is designed to slow the spacecraft allowing for a safe descent after re-entry.
Acting chairman of the NTSB Christopher Hart told a press conference today that a camera situated in the cockpit, and recovered in the probe, showed the co-pilot had moved a "feather lock-unlock lever" early, contrary to normal procedure.
The system of deployment is a two-step process, but Mr Hart said while the co-pilot unlocked the system, the second step occurred "without being commanded".
The 'feathering' system pivots the wings into a more vertical position, slowing the craft and placing into re-entry position. The craft at this point is expected to be travelling at around mach 1.4 but instead it's believed that it became active at mach 1.0.
When asked if investigators are edging towards the possibility of pilot error he said: "We are not edging towards anything at this point. We are not ruling anything out. We are looking at all of these issues to determine what was the root cause of this mishap.
"We are looking at a number of possibilities including that possibility (pilot error)."
Hart said the investigation, which could last up to a year, will be wide-ranging.
"We'll be looking at the design, the procedure. We've got many, many issues to look into much more extensively before we can determine the cause."