While performing a mission, multiple Unmanned Aerial Vehicles (UAVs) need to avoid each other to prevent collisions among them. In this paper, we design a collision avoidance algorithm to resolve the conflict among UAVs that are on a collision course while flying to their respective destinations. The collision avoidance algorithm consist of each UAV that is on a collision course reactively executing a maneuver that will, as in 'inverse' Proportional Navigation (PN), increase Line of Sight (LOS) rate between them, resulting in a 'pulling out' of collision course. The algorithm is tested for high density traffic scenarios as well as for robustness in the presence of noise. © 2009 AACC.