January4, 2007: In most years, no aircraft are brought down by air-to-air missiles. Yet air forces have to maintain inventories of these missiles, and buy new ones. Thus, each year, nearly two billion dollars is spent on buying over 6,000 new missiles. Yet there have not been any breakthroughs in air-to-air missile design, just incremental improvements, for decades. Still, these missiles have been the primary air-to-air weapon since the 1970s.

The first effective air-to-air missile, the U.S. Sidewinder, is still in service. It relies on a heat seeker to detect and follow the target. Initially, the jet exhaust of the enemy aircraft was the heat source. German engineers experimented with heat seeking missiles during World War II, but the heat seeker technology wasn't yet good enough. A decade later, it was. This is a common pattern with high-tech weapons. The basic concept is usually ready to go before the technology is.

Years of small improvements have paid off. Today's Sidewinder is far more capable. The first Sidewinders, which entered service 51 years ago, scored a hit about 12 percent of the time. This rose to 16 percent in the 1970s, and by the 1980s, improvements in the guidance system, got that up to 80 percent. Over 110,000 Sidewinders have been produced so far. It's the most successful air-to-air missile, with at least 270 kills. The Russian version of Sidewinder, the AA-2, was actually a reverse engineered Sidewinder. During the late 1950s, as Chinese and Taiwanese jets fought with each other over the Taiwan Straits, the U.S. provided Taiwan with some Sidewinders, mainly to see how the missile would perform in combat. There, in 1958, the Sidewinder scored it's first kill against a Chinese MiG-17. But in another battle, a Sidewinder hit a Chinese MiG, but didn't explode. The Chinese aircraft made it back to base, the largely intact Sidewinder was removed and given to Russian engineers, who carefully took it apart and used that knowledge to build the AA-2.

The first Sidewinder (AIM-9B) was 9.28 feet long, weighed 156 pounds and had a max range of five kilometers . The most current one, half a century later (AIM-9X) is 9.5 feet long, weighs 191 pounds and has a max range of 18 kilometers. The latest version can go after the target from all angles, while the AIM-9B could only be used from directly behind the target. The AIM-9X is about seven times more likely to bring down the target than the AIM-9B.

Some heat-seeking air-to-air missiles have a range of up to 30 kilometers. But for all practical purposes, it's rare to get a hit beyond ten kilometers. For longer range kills, you need a radar guided missile. These were developed about the same time as the Sidewinder, but the technology took longer to mature (and become reliable.) This didn't really happen until the 1980s, when the 1950s Sparrow (AIM-7) got "perfected", and then, in the 1990a, when the U.S. AMRAAM (AIM-120) arrived. Actually, the U.S. Navy developed a long range, radar guided missile (the AIM-54 Phoenix), in the 1970s. But it was too heavy (half a ton) and expensive (a million dollars each) for wide scale use. The navy justified the cost because of the need to keep missile equipped Russian bombers away from American aircraft carriers.

The radar guided missiles have an effective range of over a hundred kilometers, although in practice, most of them achieve their kills at ranges closer to fifty kilometers. As the quality of the radar guided missiles continues to improve, it is likely that this type of missile, and not the shorter range heat seekers, will become the principal air-to-air weapon. While most fighters are still equipped with cannon, it is the missiles that do most of the damage in air-to-air combat. The longer range of the radar guided missile is fundamentally changing air warfare, as the best way to defend against these missiles is to have good electronic warfare gear. This is expensive, and must be constantly updated. Those nations that cannot afford to keep up in the ECM race, become target practiced for opponents equipped with radar guided missiles.

The heat seekers are still a lot cheaper than radar guided missiles (costing about a third as much), but if you can't get close enough to use them, it's false economy.