A defense system for protecting a static structure, such as a building in an urban environment, from attack from an aircraft is provided. The air defense system includes at least one launching device for discharging a fluid payload at an incoming aircraft. Each launching device is mounted to an exterior wall of the static structure. In a preferred embodiment, the launching device is a water cannon. In a typical system, an array of launching devices are mounted to an exterior wall of the static structure which may be subject to attack from an aircraft.