The surviving pilot of the SpaceShipTwo crash on 31 October has told investigators that he was unaware the co-pilot had unlocked a system that rotates the tail feathers of the vehicle moments before an in-flight break-up, the US National Transportation Safety Board (NTSB) says.

NTSB investigators have focused on video and telemetry showing that co-pilot Mike Alsbury prematurely unlocked the tail feather rotation system as SpaceShipTwo accelerated through Mach 1.

The test card on Alsbury’s knee stated that the tail feathers should not be unlocked until SpaceShipTwo’s speed had reached at least Mach 1.4.

Alsbury was killed by the in-flight break-up of SpaceShipTwo at 55,000ft.

Pete Siebold told investigators he survived when his seat was ejected by the in-flight break-up. He then “unbuckled from his seat at some point before the parachute deployed automatically”, the NTSB says.

The NTSB has completed the on-scene investigation of the crash location in the Mojave Desert of California. The recovered wreckage of SpaceShipTwo is now stored in a secure location, the NTSB says.

As SpaceShipTwo was performing a flight test, the in-flight break-up was observed by telemetry gathering more than 1,000 parameters per second and multiple cameras inside SpaceShipTwo, the mothership WhiteKnightTwo and on the ground.

A group of NTSB investigators will assemble next week at the board’s recorders laboratory to evaluate the video footage.

Virgin Galactic has vowed to complete assembly and begin flight testing of the second SpaceShipTwo by April. The space tourism company, which collaborated with Scaled Composites, has acknowledged that about 24 of more than 700 deposit holders of suborbital launch tickets costing $250,000 each have requested refunds.