The AGM-84H/K SLAM-ER (Standoff Land Attack Missile-Expanded Response) is an advanced stand off precision-guided, air-launched cruise missile produced by Boeing Defense, Space & Security for the United States Armed Forces and their allies. Developed from the AGM-84E SLAM (Standoff Land Attack Missile, itself developed by Boeing Integrated Defense Systems from the McDonnell Douglas Harpoon antiship missile), the SLAM-ER is capable of attacking land and sea targets medium to long range (over 155 nautical miles/270 km maximum). The SLAM-ER relies on the Global Positioning System (GPS) and infrared imaging for its navigation and control, and it can strike both moving and stationary targets.The SLAM-ER can be remotely controlled while in flight, and it can be redirected to another target after launch if the original target has already been destroyed, or is no longer considered to be dangerous (command guidance). The SLAM-ER is a very accurate weapon; as of 2009 it had the best circular error probable (CEP) of any missile used by the U.S. Left 84H right 84K