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 and can now effectively do things its inventors never imagined. 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. 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 even after the pilot turns to do something else. The max range of the X-2 has been extended to 35 kilometers meaning that it can be fired at a target the pilot cannot see. This is done using the radar, which enables the pilot to send the X-2 to the general vicinity of the target and let the heat seeker take over from there.
The X-2 version also makes improvements in the warhead fuze and other components. As impressive as all these new features are most have already shown up 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 actually performing as expected in combat. Over 6,000 X model Sidewinders have been built or ordered since it entered service in 2003. Block II (X-2) completed development in 2009 but unanticipated technical problems delayed mass production until 2015.