In 2001, a bunch of U.S. smart bombs, guided by satellite GPS signals, all missed the target by the same distance, and in the same direction. U.S. weapons experts feel that it was a programming error on the part of the bomb technicians. But there's also the possibility that the Iraqis were using GPS jammers. The GPS signal is a weak one, and easily jammed. For several years, American smart bomb manufacturers have been working on making their smart bomb GPS guidance systems "jam proof", but weapons with this feature have not been put in service yet. Several nations advertise GPS jammers for sale, including Russia. And the basic technology for a GPS jammer is simple enough for Iraq to build it's own jammer. It's interesting to note that U.S. GPS smart bombs have a less accurate (but unjamable) backup guidance system. Did the Iraqis jam our GPS smart bombs? This "problem" with these bombs only happened once. But perhaps the Iraqis were just testing their jammers to see if they worked. A really clever GPS jammer would not trigger the backup guidance system. If the Iraqis have built (or bought) such a system, they are going to save it for a major attack by the U.S. If the Iraqis don't have such a system, someone does, or will. And American pilots will eventually have to deal with it.