1. A network controller for controlling a telecommunications network comprising a plurality of vehicles each including a telecommunications device, the network controller comprising: a network configuration database, containing data representing a configuration of the network; an assets database, containing for each of the plurality of vehicles (i) data representing planned movements of the vehicle in a geographic area, the vehicle having a planned route from a first location to a second location, and (ii) data representing parameters for acceptable variation in the planned route, wherein, for the vehicle, the parameters for acceptable variation in the planned route comprise an operational limitation for the vehicle, wherein the parameters for acceptable variation constrain an amount of variation in the planned route; an information exchange requirement (IER) database, containing data representing expected future network loading; an optimisation engine configured to calculate from the data stored in the network configuration database, assets database and IER database, a set of routes for the plurality of vehicles that optimises, subject to the parameters for acceptable variation, an availability of the telecommunications network in the geographic area; and a tasking-order dispatcher, configured to generate tasking orders for transmitting to the plurality of vehicles from the set of routes calculated by the optimisation engine.