Aircraft self-separation is the capability of an aircraft maintaining acceptably safe separation from other aircraft without following instructions or guidance from a referee agent for this purpose, such as air traffic control. In its simplest forms, it can be described by the concept of see and avoid, in the case of human-piloted aircraft, or sense and avoid, in the case of non-human piloted aircraft (such as UAVs). However, because of several factors such as weather, instrument flight rules and air traffic complexity, the self-separation capability involves other elements and aspects such as rules of the air, communication technologies and protocols, air traffic management and others.