Two of Richard Branson's space tourism planes—SpaceShipTwo and WhiteKnightTwo—lifted off on their first test flights in nine months today, but at some point during the test SpaceShipTwo suffered what Virgin is calling an "in-flight anomaly," killing one pilot and injuring another. Authorities confirmed the casualty in a press conference this afternoon.

UPDATE (5:05 p.m.): A local sheriff noted in today's press conference that the pilot who died was "obviously deceased immediately" while the injured pilot had "major injuries." Neither pilot has been named, and the current condition of the injured pilot was not disclosed.

The sheriff also noted that the crash site is along a "spread out" area.

Virgin Galactic first reported the issue on its official Twitter account.

It had tweeted only six minutes prior that the plane was airborne.

But in today's press conference, officials noted that the difference between the separation of SpaceShipTwo from WhiteKnightTwo, its mother plane, and the "anomaly" was only two minutes. It separated at 10:10 local time and was in distress at 10:12 local time.

Per NBC, SpaceShipTwo stays attached to WhiteKnightTwo until it reaches a certain altitude, at which point it detaches and begins flying on in its own. The network also reported that today's test flight was delayed due to weather:

Friday's test got off to a slow start. SpaceShipTwo spent more than three hours on the Mojave runway, slung beneath its WhiteKnightTwo mothership, while the ground team assessed whether the weather was right for flight. The go-ahead was finally given for takeoff at 9:19 a.m. PT (12:19 p.m. ET).

It took WhiteKnightTwo about 45 minutes to get to 50,000 feet, the altitude at which it released SpaceShipTwo for free flight.

SpaceShipTwo is piloted by two people, and according to a local news report based on scanner traffic, one pilot is dead while the other was being transported via helicopter for treatment:

Scanner traffic indicated there was one fatality in the plane crash. Virgin Galactic previously announced that the rocket plane had "experienced an in-flight anomaly" on its Twitter page. A medical helicopter carried one patient to Lancaster for treatment.

Here is a photo of what appears to be the wreckage of SpaceShipTwo.

Twitter users listening to earlier scanner traffic reported one survivor, with the other pilot being unaccounted for.

In May, Virgin announced that it was altering the fuel mixture for SpaceShipTwo.

Here is video of a SpaceShipTwo test flight from January.

[image via AP]