When in August 1957 the US Navy needed an advanced ASW/maritime patrol aircraft, the urgency was highlighted by the fact that they were prepared to accept a development of an off-the-shelf civil aircraft to meet the requirement. Lockheed proposed a developed version of the L-188 Electra, gaining an initial research and development contract on 8 May 1958. The third Electra airframe was modified as an aerodynamic prototype for early evaluation by the US Navy, flying from Burbank in August 1958. This was followed by the Lockheed YP3V-1 operational prototype, late named Orion, which first flew on 25 November 1959. The first production P3V-1 was flown on 15 April 1961, with initial deliveries being made to US Navy Patrol Squadrons VP-8 and VP-44 on 13 August 1962, by which time the type had been redesignated the P-3. Retaining the basic airframe structure of the Electra, the new aircraft differed by having a fuselage shortened by 2.24m and modified to incorporate a large weapons bay together with new avionics an,d utility systems. Mines, depth-bombs, torpedoes or nuclear devices can be accommodated in the weapons bay, and there are 10 under-wing pylons for a variety of stores. The major changes in the 30 years since the Orion entered service have been in avionics equipment and capability, and more than 640 have been built to date, with the type continuing in production (now at Marietta, Georgia) until 1995/56 for South Korea, who ordered eight P-3C Update Ills in December 1990. Other Orions are in service in Australia, Iran, the Netherlands, New Zealand, Norway, Pakistan, Portugal, Spain and in the USA with the Navy, the Customs Service, NASA and NOAA. Potential operators, probably of surplus USN aircraft, remain Thailand and Greece. Following the assembly in Japan of four P-3C aircraft from Lockheed-built components, over 100 of the type is being licence-built by Kawasaki for the Japanese Maritime Self-Defence Force. In addition, 21 examples of a derived version known as the CP-140/140A were delivered to the Canadian Forces.