This paper addresses the problem of enabling Unmanned Aircraft Systems (UAS) to avoid mid-air collisions during path planning applications. We propose an improved strategy that allows the UAS to negotiate obstacles encountered during flight, while keeping the objective of finding a feasible path towards its destination. Our method computes multiple steps along the UAS's path based on GPS coordinates, a strategy which we refer to as dynamic waypoints generation. When a risk of collision is encountered, new dynamic waypoints are generated by taking into account the obstacle's planar coordinates, as well as an approximate circular envelope around it, which allows addressing a most type of obstacle's shapes. Real-time experiments performed outdoors with a holonomic UAS are provided, demonstrating the effectiveness and reliability of the proposed strategy.