An air-to-air missile (AAM) is a missile fired from an aircraft for the purpose of destroying another aircraft. AAMs are typically powered by one or more rocket motors, usually solid fueled but sometimes liquid fueled. Ramjet engines, as used on the Meteor, are emerging as propulsion that will enable future medium-range missiles to maintain higher average speed across their engagement envelope. Air-to-air missiles are broadly put in two groups. Those designed to engage opposing aircraft at ranges of less than 16 km are known as short-range or "within visual range" missiles (SRAAMs or WVRAAMs) and are sometimes called "dogfight" missiles because they are designed to optimize their agility rather than range. Most use infrared guidance and are called heat-seeking missiles. In contrast, medium- or long-range missiles (MRAAMs or LRAAMs), which both fall under the category of beyond-visual-range missiles (BVRAAMs), tend to rely upon radar guidance, of which there are many forms. Some modern ones use inertial guidance and/or "mid-course updates" to get the missile close enough to use an active homing sensor. The concepts of air-to-air missiles and surface-to-air missiles are very closely related, and in some cases versions of the same weapon may be used for both roles, such as the ASRAAM and Sea Ceptor. History The air-to-air missile grew out of the unguided air-to-air rockets used during the First World War. Le Prieur rockets were sometimes attached to the struts of biplanes and fired electrically, usually against observation balloons, by such early pilots as Albert Ball and A. M. Walters. Facing the Allied air superiority, Germany in World War II invested limited effort into missile research, initially adapting the projectile of the unguided 21 cm Nebelwerfer 42 infantry barrage rocket system into the air-launched BR 21 anti-aircraft rocket in 1943; leading to the deployment of the R4M unguided rocket and the development of various guided missile prototypes such as the Ruhrstahl X-4. The US Navy and US Air Force began equipping guided missiles in 1956, deploying the USAF's AIM-4 Falcon and the USN's AIM-7 Sparrow and AIM-9 Sidewinder. Post-war research led the Royal Air Force to introduce Fairey Fireflash into service in 1957 but their results were unsuccessful. The Soviet Air Force introduced its K-5 (missile) into service in 1957. As missile systems have continued to advance, modern air warfare consists almost entirely of missile firing. The use of beyond-visual-range combat became so pervasive in the US that