What made the Lockheed P-3 Orion unique among other U.S. Navy aircraft was its MAD Boom—the unique tail stinger that magnetically detects submarines. The first production version of this maritime surveillance aircraft with four turboprop engines was introduced in April 15, 1961. Over the years, it saw numerous design upgrades, especially to its electronic packages. In 1969, Lockheed came up with the definitive version of the P-3—the P-3C Orion, which was equipped with modern APS-115 radar system. This model was involved in several operations, including the Operation Iraqi Freedom, Desert Storm, and Operation Desert Shield. This aircraft served the Royal Australian Air Force, German Navy, Republic of China Navy, and Japan Maritime Self-Defense Force. Despite this huge number of military and civilian operators, the US Navy remains to be the largest operator of the P3C Orion.