The U.S. Air Force is increasing it's order for the new AGM-158A JASSM (Joint Air-to-Surface Standoff Missile) from 3600 to 4900. Each missile will cost less than $500,000. JASSM is a one ton air launched missile with a range of about 400 kilometers. It uses GPS, inertial guidance and pattern recognition for precise attacks on targets. One target JASSM was designed for was Russian long range anti-aircraft missile systems, like the S-300 (SAM-10) series. JASSM is seen as the best weapon for taking out all sorts of enemy air defenses before sending in additional bombers equipped with shorter range JDAM. North Korea and China both have extensive air defense systems that could be taken down with a massive JASSM attack. B-52s can carry a dozen or more JASSMs per sortie. An improved version, the AGM-158B, with a better engine, will have a range of 1,000 kilometers. Both versions carry a half ton warhead, which can contain all explosives or cluster munitions. AGM-158A is to enter service by the end of 2003.