Abstract: A ground-based flight simulator having a television type terrain visual display with simulated weather conditions. The visibility of the terrain image is varied over the picture area to simulate ground fog and cloud conditions, either one alone or both together. Either weather condition provides a zone of transitional visibility, i.e., spatially changing visibility between spaced zones of uniform visibility, e.g., between one of uniformly clear visibility and another zone of uniformly zero visibility. The transitional zones may be varied in width according to aircraft pitch and the entire weather pattern rotated, together with simulated terrain, according to aircraft roll.