Saudi Arabia and South Korea recently ordered over 150 AIM-9X Block 2 air-to-air heat seeking missiles. Both nations have used this missile for decades and are satisfied customers. They are not alone. The AIM-9X Block 2 is the latest version of the Sidewinder, a missile that has come a long way since it first appeared in the 1950s. In the last 25 years these short-range heat-seeking missiles have accounted for some 90 percent of losses in air-to-air combat. Sidewinder still dominates the market, despite a lot of competition from the likes of IRIS-T, ASRAAM, Magic, Python, Molinya, and several Chinese clones of foreign designs.
There are not only a lot of different heat-seekers out there, they offer a wide variety of features. Sidewinder has managed to dominate the field by concentrating on the most useful, workable, and popular features. For example, the 9X-2 can lock-on-after-launch. That is, the missile can be fired and then directed to a target via a datalink. That means it can be fired at ground targets or at an enemy aircraft behind you. The X-2 version also makes improvements in the warhead fuze and other components. As impressive as all these features, most are already found in similar missiles made in several other countries (including Russia and China). In effect, the X-2 version is just keeping up. What the U.S. sells, in addition, is an impressive track record of reliability and the high probability of actually performing as expected in combat. Over 4,000 X model Sidewinders have been built since it entered service in 2003. Block II (X-2) entered service four years ago.
The AIM-9 is a heat seeking missile and the heat sensors have become much more sensitive since the first AIM-9s. The current versions of the missile work by detecting a heat source at the point where the pilot is looking. This is done using the JHMCS (Joint Helmet Mounted Cueing Systems), which allows a pilot to see, displayed on his visor, critical flight and navigation information. Sort of like a see-through computer monitor or HUD (Head Up Display). Most importantly, the pilot can turn his head towards a target, get an enemy aircraft or ground target into the crosshairs displayed on the visor, and fire a missile that will promptly go after the target the pilot was looking at. For Sidewinder the pilot has to be looking at something giving off enough heat to catch the attention of the missile's heat sensor. With the X-2 the pilot can launch the missile before he has located the target via the JHMCS, saving a critical few seconds.