(CNN) -- The surviving pilot of Virgin Galactic SpaceShipTwo told authorities he was unaware the feather system had been unlocked early by his co-pilot. 

The spaceship disintegrated 45,000 feet above the Mojave Desert on October 31, killing co-pilot Michael Tyner Alsbury and injuring co-pilot Peter Siebold, who managed to parachute to the ground. 

Siebold was interviewed last week by the National Transportation Safety Board. He described being "extracted from the vehicle as a result of the break-up sequence and unbuckled from his seat at some point before the parachute deployed automatically," according to a release from the NTSB. 

Earlier this month, the NTSB tweeted that Alsbury "moved the lock/unlock handle into unlock position." 

...the copilot, who was in right seat, moved the lock/unlock handle into unlock position; he did not survive accident. #SpaceShipTwo 

But that mishap alone doesn't explain why the feathering started, since no one moved the feathering handle. 

During feathering, two pieces on the back of the vehicle -- the "feathers" -- lift up perpendicular to the spaceship, making the vehicle look as though it's arching its back as it descends. 

The wreckage has been recovered and will be used for follow-up examinations. 

Test pilot's workplace a cold, harsh environment 


What does feathering make the spaceship look like when it's coming down?
During feathering, two pieces on the back of the vehicle -- the "feathers" -- lift up perpendicular to the spaceship, making the vehicle look as though it's arching its back as it descends. 