Cruise missiles are essentially a flying jet engine that is armed with a warhead; some can fly at low altitudes to escape radar detection and air defenses. They require a boost, either via rocket launch or release from a high-speed aircraft, to get air flowing through an inlet to spin up their engine. As they fly, they compress that incoming air, mixing it with fuel and burning the mixture to produce thrust. The U.S.’s latest long-range cruise missile, the nuclear-armed AGM-181, reportedly can fly more than 1,500 miles at subsonic speeds using a conventional jet engine.