A multi mode aircraft beacon light comprises a mounting portion for mounting the multi mode aircraft beacon light to an aircraft fuselage; at least one visible light source for emitting a visible beacon light output; a plurality of infra-red light sources for emitting an infrared beacon light output; an orientation sensor; and a controller, coupled to the orientation sensor for receiving an orientation sensor signal from the orientation sensor. The controller is configured to determine a mounting orientation of the multi mode aircraft beacon light from the orientation sensor signal, wherein the mounting orientation is indicative of whether the multi mode aircraft beacon light has an upper fuselage mounting position or a lower fuselage mounting position; and to selectively operate the plurality of infrared light sources, depending on the mounting orientation of the multi mode aircraft beacon light.