From Virgin Galactic on SpaceShipTwo:
Windows in the passenger compartment will be 13 inches (33 centimeters) wide by 17 inches (43 centimeters) tall.
IMO that's enormous for an airplane, especially for a spaceplane! But, wouldn't such large windows cause problems? The Concorde had particularly small windows (passengers say that it's almost passport book sized) to maintain the integrity of the airframe and cabin pressure if a window happened to crack at 60,000 feet AMSL.
But wouldn't such a large window cracking at 110 km AMSL on SpaceShipTwo definitely cause cabin pressure to equalize to atmospheric pressure in seconds? What redundancy does SS2 have to prevent catastrophe in such an event?