December17, 2006: The U.S. Department of Defense ordered another 375 AIM-9X Sidewinder air-to-air missiles. The order includes 153 training missiles. These have no motors, and are not launched. That's because the Sidewinder is a short range (usually under ten kilometers) missile that requires the missile heat seekers to detect the heat from an enemy aircraft (and alert the using pilot), before it is launched. Thus the training missiles enable pilots to practice getting in a good firing position. The actual missiles cost about $200,000 each. The training missiles are basically real missiles, minus the solid rocket fuel, and cost a bit less.