Abstract: The invention provides an airborne passive decoy system for use in the radio waveband, the system comprising a controllable aerial propulsion unit and one or more retroreflectors, wherein the one or more retroreflectors are mounted on, contained within or otherwise borne by the controllable propulsion unit, and wherein the system is configured such that the one or more retroreflectors can be deployed as a decoy at a desired location and/or time. The system is an integral system which does not rely on tethers, cables or suchlike. Related methods and uses are also provided.