Abstract: An aircraft lighting system is disclosed in which conventional visible light sources at the exterior of an aircraft are provided with optical filters which block infra red light. In this way, it is made possible to use visible external lighting (required by Civil Aviation Authority regulations) during training exercises involving infra red sensitive night vision goggles, which would otherwise be dazzled by the infra red output of the visible lighting. Also disclosed are means of selectively controlling both visible and I.R. light sources using a single existing cable.