A cruise missile is a guided missile used against terrestrial targets, so called because the major portion of its flight path is conducted at cruise speed (i.e., approximately constant velocity). Cruise missiles are designed to deliver a large warhead over long distances with high accuracy (i.e. small circular error probability). The dynamics of cruise are a result of aerodynamic lift (force), and the equality of the thrust or propulsion forces against aerodynamic drag and as a result there is no acceleration. Modern cruise missiles are capable of travelling at supersonic or high subsonic speeds, are self-navigating, and are able to fly on a non-ballistic, extremely low-altitude trajectory. They are distinct from unmanned aerial vehicles (UAV) in several ways: the cruise missile is a single use weapon which is always sacrificed in the mission; it is not intended to provide aerial reconnaissance; and the warhead is integrated directly into the hull of the vehicle and cannot be separated.