The Lockheed Martin P-3 Orion is a land-based, long range anti-submarine warfare (ASW) patrol aircraft. It has advanced submarine detection sensors such as directional frequency and ranging (DIFAR) sonar buoys and magnetic anomaly detection (MAD) equipment.

Developed from the Lockheed L-188A Electra, the third Electra prototype (N1883) was modified to the aerodynamic prototype of Model 185 (later P-3 Orion), complete with a dummy MAD-boom and a simulated weapons bay.

The P-3 can be fitted with a variety of sophisticated detection equipment. Infrared and long-range electro-optical cameras plus special imaging radar allow it to monitor activity from a comfortable distance. It can stay aloft for extremely long periods, and its four powerful Allison T-56-A-14 engines can fly at almost any altitude. And like all good hunters, it has no problem carrying weapons.

Early P-3A aircraft were equipped with a variety of sensors and armaments. Sensor equipment included radar, sonar (Jezebel/Julie), identification friend or foe (IFF), electronic sensing measures (ESM), a diesel exhaust sniffer, a magnetic anomaly detector (MAD), and a powerful searchlight. A typical first generation P-3A crew consisted of three pilots, two flight engineers, a radio operator, an electronic technician, an ordinance specialist, four sensor operators, a tactical coordinator, and a navigator. Armaments carried included sonarbouys, mines, depth bombs, and torpedoes. Typical ASW or patrol missions would last 8 to 10 hours.

In 1964 Lockheed came up with an improved version of the P-3 Orion which was designated the P-3B. The P-3B featured improved engines (no water injection), a modernized sensor suite, and the capability to fire the Bullpup air to surface missile. The diesel exhaust sniffer, which had been notoriously unreliable, was not installed in the P-3B and was eventually removed from all P-3A models. One sensor operator, the man who operated the diesel sniffer, was removed from the Orion's typical tactical crew.

On 18 September 1968 the first P-3C Orion took to the air. The P-3C presented further sensor and weapon system improvements over the P-3A and P-3B. The P-3C introduced dramatically new radar and ESM systems. Many P-3C aircraft were fitted with low light television (LLTV) or an infrared detection system (IRDS) which permitted visual searches in near or complete darkness. The P-3C aircraft was configured to fire the Harpoon air to surface missile. However, the most dramatic improvement over previous versions of the Orion was that the P-3C integrated sensor and tactical data using a Univac CP-901 digital computer. The P-3C's computer system dramatically improved the efficiency of the aircraft's tactical crew. The P-3C's navigator assumed the duties of the radio operator, removing another man from the Orion's typical tactical crew.

Since its introduction in 1969, the P-3C has undergone a series of configuration changes to implement improvements in various mission and aircraft systems through updates to the aircraft. These changes have usually been implemented in blocks referred to as "Updates."

Update I, introduced in 1975, incorporated new data processing avionics and software, while Update II in 1977 featured an infrared detection system, a sonarbouys reference system, the Harpoon anti ship missile and a 28-channel magnetic tape recorder/reproducer.

Technical Evaluation (TECHEVAL) for P-3C Update III Aircraft began in March 1981, and was completed in second quarter 1982. The Update III Program was enhanced by a Channel Expansion (CHEX) Program. CHEX doubled the number of sonar buoy channels that can be processed and has been installed in all P-3C Update III Aircraft. The P-3C still remains the most up-to-date version of the P-3 Orion. A successor aircraft from Lockheed was planned during the early 1980s which would have been designated the P7. Funding dried up for this project causing it to be cancelled in 1989. Thus, the P-3 Orion will probably continue on as the World Navy's premier antisubmarine warfare and maritime patrol aircraft through the first decades of the 21st century.

The EP-3 version was developed for electronic reconnaissance missions and was equipped with a very specialized mission equipment suite including several types of radar systems. The aerials were installed in radomes below the forward fuselage and the centre wing. Some variants are: EP-3A, EP-3B “Batrack”, EP-3E ARIES, EP-3E “Deepwell” and EP-3E ARIES II.

The P-3AEW&C “Dome” is an Airborne Early Warning and Control version of the Orion, the US Customs Service is the only operator of this version and refers to the aircraft as “Hi-tech “Drug Hunter”.