The Lockheed Martin P-3 Orion is a four-engine turboprop anti-submarine and maritime surveillance aircraft developed for the United States Navy and introduced in the 1960s. Lockheed based it on the L-188 Electra commercial airliner. The aircraft is easily recognizable by its distinct tail stinger or "MAD Boom", used for the magnetic detection of submarines. Over the years, the aircraft saw numerous design advancements, most notably to its electronics packages. The P-3 Orion is still in use by numerous navies and air forces around the world, primarily for maritime patrol, reconnaissance, anti-surface warfare and anti-submarine warfare. A total of 734 P-3s have been built, and by 2012, it will join the handful of military aircraft such as the Boeing B-52 Stratofortress which have served 50 years of continuous use with its original primary customer, in this case, the United States Navy.