The US Navy has operated the land-based P-3 Orion maritime patrol aircraft for anti-submarine warfare and anti-shipping, as well as for overland surveillance, reconnaissance, mine-laying, drug interdiction logistic, threat simulation crew training and search and rescue missions.
Although developed to counter the Soviet submarine threat, the maritime patrol force, greatly reduced in size since the end of the Cold War, finds itself in great demand in the littoral warfare environment of the early 21st century. The current front-line version is the P-3C which equips 12 active and seven reserve patrol squadrons the P-3C entered service in Baseline form in 1969 and has been upgraded since through various update configurations. Modifications to their equipment has sharpened their capabilities. The Lockheed P-3 Orion is currently in service with 15 countries.
The P-3C has a sophisticated sensor suite including the UYYS-1 acoustic sonobuoy processor and ALR-66 electronic surveilance system, plus magnethic anomaly detection gear, and infre-red detection system and a search radar. Some aircraft are equipped with the APS-137 imaging synthetic aperture radar which can display an image of its target.
P-3Cs are currently undergoing several upgrade programmes to extend airframe life until 2015 and to improve their mission suites and armament. The US Navy is gradually upgrading most P-3Cs to an Update III Common Configuration that will be the Fleet standard. The Anti-Surface Improvement Program (AIP) is planned for 146 P-3Cs and includes enhancements in command, control, communications and intelligence, over the horizon targeting and survivability. New weapons such as Maverick, SLAM and SLAM-ER give the P-3 as potent stand-off land attack capability.
The first AIP P-3C entered service in 1998. Twelve Ep-3Es serve in the long-range reconnaissance role, equipped with the Aries II mission avionics suite. US Navy Special Projects Units fly small numbers of modified P-3Bs and P-3Cs for tactical and strategic intelligence collection. P-3A/Bs serve in the maritime patrol role with Argentina, Greece, Norway, Portugal, Spain and Thailand while P-3Cs serve with Australia, Iran, the Netherlands, Norway, Japan, Pakistan and South Korea. Japan operates 110 Kawasaki-built P-3Js while Canada has 18 CP-140 Auroras fitted with different mission avionics to US Navy P-3Cs.
The US Navy's Orion fleet is due to be replaced with the new Boeing P-8 Poseidon. First aircraft are expected to enter service in 2013.