Abstract: Measurements of the instantaneous position and speed of an aircraft are incorporated in co-operation messages regularly broadcast to other aircraft by radio. The device fitted on the aircraft, flying under visual flight rules, analyzes the data contained in the co-operation messages received from other aircraft and its own trajectory in order to identify potential risk of collision. The pilot is alerted to these potential risks of collision, advantageously in voice form, in messages identifying the direction in which the other aircraft is visible as well as an estimation of the time remaining until the potential collision.