The co-pilot who was killed in the crash of Virgin Galactic’s SpaceShipTwo prematurely unlocked a lever to the spacecraft’s re-entry system, the National Transportation Safety Board has confirmed.

The action by Michael Alsbury, 39, may have led the spacecraft’s drag-creating “feathering” system to deploy, the NTSB said.

SpaceShipTwo broke apart over the Mojave Desert moments later on Friday, killing Alsbury and injuring the pilot, Peter Siebold, who parachuted.

Wreckage was found as far as 35 miles from the crash site.

The NTSB earlier said pilot error may have led to the test flight accident.

Christopher Hart, the agency’s acting chairman, said a “human performance group” will examine the pilots’ performance and how they interacted with the controls during the ill-fated flight. Investigators have not yet interviewed Siebold, who survived the accident but was seriously hurt.

The NTSB said the spaceship’s “feathering” system, which slows the craft upon re-entry, was unlocked too soon and deployed during the ascent stage.

It may take up to a year for the investigation to be completed.

Billionaire businessman Richard Branson has insisted that no corners had been cut to launch tourists into space and vowed Monday that the program will continue. He said the company will conduct a massive series of test flights before taking thrill-seekers into the heavens.

Branson, however, also said he and his family will go to space before the tourists do.

Meanwhile, Virgin Galactic is offering refunds to any “future astronauts,” as it refers to them, who are having second thoughts.

“We can confirm that less than 3 percent of people have requested refunds,” the company said, according to a USA Today report.

A host of celebrities — including Justin Bieber, Ashton Kutcher and Leonardo DiCaprio — are among those who shelled out deposits on $250,000 tickets, hoping to experience about six minutes of weightlessness 62 miles above Earth.