The Martin P4M Mercator, although outwardly similar to the smaller Lockheed Neptune, was designed later and developed for a different requirement. Its specific 1946 design purpose was long-range patrol and mine laying. It was a high-wing, four-engine aircraft with one jet engine and one prop engine mounted in a large engine nacelle under each wine (two turning and two burning ). The first flight was on September 20, 1946. Nineteen of the much sleeker production machines were complete in September 1950. The aircraft were utilized heavily until 1960, first as a patrol aircraft with VP-21 from 1949-1951 and then as the P4M-1Q, a spy plane with VW-1, VW-2, VW-3, VQ-1 and VQ-2. It was a natural for this mission as it was 1/3 larger, 25% faster, had longer range, and was more heavily armed than the Lockheed Neptune. Because of its mission, Cold War losses were five aircraft, one of which was shot down by the Communist Chinese where all hands were killed. Another had two engines shot out and a crewman wounded by North Korean fighters in 1959.