The small Unmanned Aerial Vehicle (UAV) has been proposed as an ideal platform for an increasing number of civilian mission roles. However, the small size of this class of UAV, while beneficial for acquisition and operational costs, presents a problem when it comes to their ability to be seen by other aircraft. Unless some means of enhancing visibility is used, the small size creates an essentially invisible entity at normal aviation visual sighting ranges and therefore an increased collision risk. In this paper, a human factors experiment is presented where the visibility of a proposed aircraft lighting system was assessed in realistic night time conditions. These results have been compared against theoretical detection range estimates based on basic photonics and the capabilities of the human vision system, and the minimum sighting distances according to current aviation regulations. Other technologies proposed to improve the detectability of the small UAV are also introduced. The outcome of this research is a proposed minimum set of safety equipment which should make the small UAV at least as safe as equivalent manned aircraft operating in the same airspace.