Today, Virgin Founder, Sir Richard Branson and SpaceShipOne designer, Burt Rutan, pulled back the hangar doors on the new WhiteKnightTwo (WK2) carrier aircraft that will ferry SpaceShipTwo and thousands of private astronauts, science packages and payloads on the first stage of the Virgin Galactic sub-orbital space experience.

Christened 'EVE' in honor of Sir Richard’s mother, who performed the official naming ceremony.
It is the world’s largest all carbon composite aircraft and many of its component parts have been built using composite materials for the very first time. At 140 ft, the wing spar is the longest single carbon composite aviation component ever manufactured.
Driven by a demanding performance specification set by Virgin Galactic, WK2 has a unique heavy lift, high altitude capability and an open architecture driven design which provides for maximum versatility in the weight, mass and volume of its payload potential. It has the power, strength and maneuverability to provide for pre space-flight, positive G force and zero G astronaut training as well as a lift capability which is over 30% greater than that represented by a fully crewed SpaceShipTwo. The vehicle has a maximum altitude of over 50,000 ft and its U.S. coast-to-coast range will allow the spaceship to be ferried on long duration flights.

An all carbon composite vehicle of this size represents a giant leap for a material technology that has already been identified as a key contributor to the increasingly urgent requirement by the commercial aviation sector for dramatically more fuel efficient aircraft. Powered by four Pratt and Whitney PW308A engines, which are amongst the most powerful, economic and efficient available, WK2 is a mold breaker in carbon efficiency and the epitome of 21st century aerospace design and technology.

The twin fuselage and central payload area configuration allow for easy access to WK2 and to the spaceship for passengers and crew; the design also aids operational efficiencies and turnaround times. WK2 will be able to support up to four daily space flights, is able to carry out both day and night time operations and is equipped with a package of highly advanced avionics.
More details on the Virgin Galactic site. See a video of the unveiling of WhiteKnightTwo on BBC News.