Many works of fiction have featured UFOs. In most cases, as the fictional story progresses, the Earth is being invaded by hostile alien forces from outer space, usually from Mars, as depicted in early science fiction, or the people are being destroyed by alien forces, as depicted in the film Independence Day. Some fictional UFO encounters may be based on real UFO reports, such as Night Skies. Night Skies is based on the 1997 Phoenix UFO Incident.