One of WhiteKnightTwo's two fuselages is designed as an exact replica of the cabin of SpaceShipTwo, which features seating for six passengers and two pilots. It has ample space for floating and features two large windows for each passenger.
Passengers can remain seated in their spacious, reclinable seats or when in a zero-gravity environment, choose to float around the cabin and look out the windows at the sky. This is because a secondary role of WhiteKnightTwo is to train passengers for eventual zero-g experiences on SpaceShipTwo.
The second fuselage on WhiteKnightTwo provides a similar experience for passengers who are not preparing for a trip on SpaceShipTwo.