Image processing and filtering are essential elements for the visual tracking system in an unmanned aerial vehicle. This paper presents visual tracking methodology based on particle filtering in the framework of a fast implementation of the Chan-Vese active contour model. The fast implementation greatly improves the computational time of the segmentation process. We have tested particle filtering using this fast active contour model, and the filtering algorithm has shown the ability to robustly track an aerial target under varied conditions. The computational speed of the algorithm has allowed us to employ it for formation flight among UAVs. We have also demonstrated the utility of the filtering algorithm for multiple target tracking in the presence of occlusions.