The Lockheed 188A Electra first flew on 06 December 1957. The transport, a four-engine turboprop airliner of short-to-medium range with a maximum capacity of 99 passengers, received its type certificate on 22 August 1958, and entered scheduled airline service with Eastern Air Lines on 12 January 1959.
In August 1957, the US Navy called for design proposals for a new advanced aircraft for maritime patrol and antisubmarine warfare (ASW) to replace the aging P-2 Neptune. The Navy strongly suggested that a variant of an existing aircraft or one in the advanced design stage be used to save cost and permit rapid introduction into fleet service. Accordingly, Lockheed proposed a military version of the Electra. Development of the Electra to provide the Navy with replacements for its land-based Lockheed P2V Neptunes and Martin P5M Marlins was initiated in 1957, before the first flight of the turboprop-powered airliner. With its design meeting fully the requirements of the Navy, Lockheed easily won the design competition.
In April 1958, the Navy announced that the Electra derivative had won the competition. Lockheed was awarded an initial research and development contract in May 1958, and first flew the Orion's aerodynamic prototype on 19 August 1958. Known initially as the P-3V, the aircraft was redesignated in 1962 as the P-3 Orion. The Orion retained the wings, tail unit, basic fuselage structure, power plant, and many subsystems of the Electra, although its fuselage was about 7 ft. shorter than the Electra's.