The use of large numbers of unmanned air vehicles in a given air space presents a challenge for conventional air traffic control methods. Flocking (or schooling, swarming or herding) in nature arises when mobile organisms find benefit in living at high densities. The present paper applies rules of flocking (cohesion, alignment, separation, and migration) to the problem of managing the flight of a number of autonomous unmanned air vehicles. A six-degree of freedom aerodynamic model of an existing UAV is used to simulate the flocking flight vehicles. It is found that application of the cohesion and alignment rules is sufficient to generate true flocking behaviour in that the flight vehicle density is increased and the flock members converge on a common heading. Increasing rule strength reduces the time taken to achieve flocking behaviour. However increasing rule strength too far leads to oscillatory or unstable flight paths. It is found that flock behaviour can be adequately described using the time histories of two statistical parameters: the mean radius between flock members and the standard deviation of the flock members’ heading angles.