1. A collision avoidance system, comprising: a receiver configured to receive navigational data regarding intruding aerial vehicle and own aircraft; storage configured to store a plurality of predefined escape trajectories, and a processor configured processing means arranged to compare at least a subset of the predefined escape trajectories with a presumed trajectory of the intruding aerial vehicle, and to select one of the predefined escape trajectories based on said comparison, wherein the predefined escape trajectories are pre-simulated, each escape trajectory being associated to a set of navigational data and to an escape manoeuvre direction.