The invention relates to a light sign (10) for displaying an instruction and/or guidance for ground airplane traffic at an airport, comprising a casing (20) with a transparent display panel (21) for representing an instruction and/or guidance symbol (Z), and a light source arranged inside the casing (20) with at least one luminescent diode (32) for illuminating the display panel (21). A diffusion panel (22) is made for scattering and/or back-scattering incident light, wherein the light source is arranged between the display panel and the diffusion panel. The at least one luminescent diode (32) is aligned on the diffusion panel (22) so that the display panel (21) is not illuminated directly, but indirectly by back-scattering of the light emitted from the at least one luminescent diode by the diffusion panel (22).