Methods and systems herein relate to unmanned aerial vehicles (UAVs) avoiding collisions by interacting with servers. Some embodiments of a method include receiving, by an unmanned aircraft system (UAS) traffic management (UTM) server one or more intended trajectories from one or more UAVs; determining, by the UTM server one or more conflicts based on the intended trajectories intersecting over a region monitored by the UTM server; and communicating, by the UTM server the one or more conflicts, the communicating includes assigning a value to each of a plurality of three-dimensional (3D) grid cells representing the region monitored by the UTM server, each value representative of a potential for conflict associated with a grid cell; and transmitting, to the one or more UAVs, value data associated with the plurality of grid cells.