Air combat is not an organized affair. When fighters (or bombers) are targeted, they tend to evade - a lot. In the early days, this was a big reason why missiles like the AIM-7 Sparrow performed miserably in combat. The Sparrow had decent range (70 kilometers), but against fighters, it performed poorly. In Desert Storm, only 36 percent of Sparrows hit their targets. Why? It was easy to evade and decoy due to its semi-active radar-homing system. The AIM-54 Phoenix was another missile that was impressive on paper (150-kilometer range, speed of Mach 5, active radar homing), but it was really only good against bombers. Jamming also had the ability to throw these earlier missiles off, making it almost impossible to hit an agile fighter trying to get out of the way.
In the 1980s, the limitations of these missiles were known, and new electronics were being designed to try and deal with the problem. Very little is revealed about the electronics, which include better radars, the ability to home in on jammers, and even the use of electronic counter-countermeasures (ECCM), which are able to defeat jamming and decoys. In the 1980s, a new concept in air-to-air missile performance emerged, that of the "no-escape zone". The name is pretty self-explanatory - it is a zone in which an aircraft will be unable to escape from a missile that is fired at it.
The first missile in the West to really focus on the biggest possible "no-escape zone" was the AIM-120 AMRAAM. This was a missile whose initial versions matched the range of the Sparrow. The difference was that the AMRAAM is not only more maneuverable, but it also employed an active seeker and a "home on jam" capability. This focus has proven itself over Iraq and the former Yugoslavia. You will not hear much about the precise capabilities - much of these improvements will never be released for public consumption. When it comes to air-to-air missiles, what the other side doesn't know will hurt them. - Harold C. Hutchison (email@example.com)
Air-to-air missiles are things that people think they know about, but they don't know the most important things about them. For example, the known facts about air-to-air missiles are not what really matter in combat. This is no surprise. Range is probably the performance figure that is touted the most, but it is actually the least relevant figure in terms of judging a missile's capabilities in air combat.