MOJAVE - The unique, twin-fuselage WhiteKnightTwo carrier aircraft continued to expand the flight envelope with its third test flight, taking it higher, faster and for longer duration than the earlier two test flights. The aircraft is the prototype mothership for Virgin Galactic's nascent space tourism business, and will carry aloft the six-passenger SpaceShipTwo for suborbital spaceflights. In a two-and-a-half-hour test flight from the Mojave Air and Space Port on Wednesday, WhiteKnightTwo reached a maximum speed of 140 knots (161 mph) and reached an altitude of above 18,000 feet, according to a Virgin Galactic statement. The flight also successfully tested in-flight...