A communications management system for an unmanned air vehicle; wherein the communications management system is adapted for use on an unmanned air vehicle, and is arranged to selectively route data between a plurality of avionic subsystems and/or communications resources on the unmanned air vehicle and a plurality of transceivers on the unmanned air vehicle, the routes selected being determined at least in part according to a desired red and black data separation of data to be transmitted from the transceivers and/or a red and black data separation of data being received by the transceivers, the communications management system comprising: a configurable router for use on the unmanned air vehicle, the router arranged to route data between the plurality of avionic subsystems and/or communications resources on the unmanned air vehicle and the plurality of transceivers on the unmanned air vehicle; for at least one of the transceivers on the unmanned air vehicle, at least one black link for linking the router to that transceiver and/or at least one red link for linking the router to that transceiver; and a respective network interface at an interface between the router and at least one of the following: the black router-transceiver link(s), the red router-transceiver link(s), and the router-avionic subsystem and/or communications resource link(s), the network interface being configured to: apply a wrapper to the data when the data is received by the respective transceiver from outside the communications management system, wherein the wrapper provides routing information; and verify, by analysing the wrapper, that the data is data that is permitted to be passed along the respective link that the network interface is guarding when the data is sent to the respective transceiver to exit the communications management system. a configurable router for use on the unmanned air vehicle, the router arranged to route data between the plurality of avionic subsystems and/or communications resources on the unmanned air vehicle and the plurality of transceivers on the unmanned air vehicle; for at least one of the transceivers on the unmanned air vehicle, at least one black link for linking the router to that transceiver and/or at least one red link for linking the router to that transceiver; and a respective network interface at an interface between the router and at least one of the following: the black router-transceiver link(s), the red router-transceiver link(s), and the router-avionic subsystem and/or communications resource link(s), the network interface being configured to: apply a wrapper to the data when the data is received by the respective transceiver from outside the communications management system, wherein the wrapper provides routing information; and verify, by analysing the wrapper, that the data is data that is permitted to be passed along the respective link that the network interface is guarding when the data is sent to the respective transceiver to exit the communications management system. apply a wrapper to the data when the data is received by the respective transceiver from outside the communications management system, wherein the wrapper provides routing information; and verify, by analysing the wrapper, that the data is data that is permitted to be passed along the respective link that the network interface is guarding when the data is sent to the respective transceiver to exit the communications management system.