Investigations are currently on going to determine what caused the mid-air accident involving Virgin Galactic's space tourism vehicle. The company's SpaceShipTwo (SS2), which was designed to transport everyday passengers to and from suborbital space, crashed during a test flight on Oct. 31.

National Transportation Safety Board (NTSB) acting chairman Christopher Hart said that the probe on what caused the crash that has killed one of the spacecraft's pilots and threatens the fledgling space tourism industry, may take several more days, but there are already theories on what probably caused the SS2 to break up.

Among the things that are being looked at is a safety device on the spacecraft that investigators from the NTSB, which is heading the probe, said was deployed too soon. Hart said that the spacecraft's feathering system, which was supposed to be activated at Mach 1.4, was deployed early during the ill-fated test flight. The feathering system is the spacecraft's descent device and is similar to the wing flaps used by airplanes to slow for landing.

On Nov. 2, Hart said that the cockpit video revealed that Michael Alsbury, the co-pilot of the spacecraft who died in the accident, unlocked the feathering system earlier than it was designed to.

"Approximately two seconds after the feathering parameters indicated that the lock/unlock lever was moved from locked to unlocked, the feathers moved toward the extended -- the deployed position -- even though the feathering handle had not been moved," Hart said. "This occurred at a speed just above approximately Mach 1.0."

Within a short moment after the feather was unlocked, the spacecraft started to disintegrate. Hart said that the disintegration occurred two seconds after the feathering system was unlocked. Telemetry data and video data were also terminated soon after the feathering occurred.

 "Normal launch procedures are that after the release, the ignition of the rocket and acceleration, that the feathering devices are not to be moved - the lock/unlock lever is not to be moved into the unlock position -- until the acceleration up to Mach 1.4," Hart said.

Investigators said that this may possibly be the cause of the crash, but they still need to conduct further investigations before making a conclusion.

The new type of fuel used during the test flight is also speculated to have been the cause of the accident. The doomed flight used a plastic-based fuel for the first time. SS2 used to run on rubber-based fuel but Virgin Galactic decided to switch to a new fuel in May this year.

Hart, however, said that the rocket motor that ran on the new fuel ignited as planned. The propellant tanks and engine were also found intact suggesting that no explosion occurred.