When in August, 1957, the US Navy needed an advance 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 airplane to meet the requirement. Lockheed proposed a developed version of the L-188 Electra, gaining an initial research and development contract on May 8, 1958. The first production Orion was flown on April 15, 1961, with initial deliveries of the airplane being made to the Navy on August 13, 1962. Retaining the basic airframe structure of the Electra, this new airplane differed by having a fuselage shortened by 7 ft. 4 in. and modified to incorporate a large weapons bay together with new avionics and utility systems. Mines, depth-bombs, torpedoes, or nuclear devices can be accommodated in the weapons bay, and there are 10 underwing 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 had been built by the time production of the airplane ended in 1995, with the aircraft being used by several countries. The P-3C was powered by four 4,910 shp Allison T56-A-14 turboprops, with a maximum speed of 473 mph, patrol speed of 237 mph, and maximum mission radius of 2,383 miles.