Purpose - Unmanned aerial vehicles (UAVs) have a wide variety of applications such as surveillance and search. Many of these tasks are better executed by multiple UAVs acting as a group. One of the main problems to be tackled in a high-density UAV traffic scenario is that of collision avoidance among UAVs. The purpose of this paper is to give a collision avoidance algorithm to detect and resolve the conflicts of projected path among UAVs. Design/methodology/approach - The collision avoidance algorithm developed in the paper handles multiple UAV conflicts by considering only the most imminent predicted collision and doing a maneuver to increase the line-of-sight rate to avoid that conflict. After the collision avoidance maneuver, the UAVs fly to their destinations via Dubins shortest path to minimize time to reach destination. The algorithm is tested on realistic six degree of freedom UAV models augmented with proportional-integral controllers to hold altitude, velocity, and commanded bank angles. Findings - The paper shows, through extensive simulations, that the proposed collision avoidance algorithm gives a good performance in high-density UAV traffic scenarios. The proposed collision avoidance algorithm is simple to implement and is computationally efficient. Practical implications - The algorithm developed in this paper can be easily implemented on actual UAVs. Originality/value - There are only a few works in the literature that address multiple UAV collision avoidance in very high-density traffic situations. This paper addresses very high-density multiple UAV conflict resolution with realistic UAV models. © 2011 Emerald Group Publishing Limited. All rights reserved.