In order for remotely piloted aircraft systems (RPAS) to operate in unsegregated airspace, one of the most important risks to mitigate is that of the mid-air collision. The RPAS must be capable of detecting the potential for a mid-air collision and performing avoidance maneuvers at normal flight conditions and under contingency or emergency conditions. In particular, when the link is severed the RPAS will become “uncontrolled” by the remote pilot, but the loss of link does not imply the loss of the remotely piloted aircraft. A D&A system is required for safe operations of RPAS in airspace shared with other aircraft, including manned aircraft. The onboard system of an unmanned aircraft has to be equipped with an efficient detection and early risk analysis system, as well as a system assisting the pilot in making a decision or an autonomous control system able to perform a maneuver to avoid collision. Collision avoidance maneuvers should be planned by taking into account the operational specificities of the RPAS. The resolution advisory’s strength and direction could be adapted to the capabilities of the RPAS. For example, horizontal resolution advisories could be introduced for RPAS unable of reaching the vertical acceleration/speeds required for vertical resolution advisories. The selection of types of sensors, their sensitivity and range can be made by taking into account RPAS maneuverability. The traffic advisory and resolution advisory regions could be defined by the same circumstances, among others. The aim of this work is to determine an optimal trajectory of horizontal avoidance maneuver of a mini remotely piloted aircraft, minimizing the time of performing a maneuver when avoiding a manned aircraft flying at a much higher speed, guaranteeing a minimally required distance between the passing objects.