It still has a few more key hurdles to cross, but it looks like Virgin Galactic's SpaceShipTwo (a.k.a. the VSS Enterprise) is remaining on track for its first commercial flight sometime next year. The latest milestone is the spacecraft's first flight with a crew on board, which occurred on July 15th at Virgin Galactic's usual base of operations, the Mojave Air and Space Port. As with previous flights, however, SpaceShipTwo remained attached to the VMS Eve "mothership" for the duration of the flight, but it did stay aloft for more than six hours as the crew (including test pilots Peter Siebold, Michael Alsbury) went through a range of tests. Still no word on exactly when SpaceShipTwo will see its first solo flight but, barring any change in plans, that should be the next flight that takes place.