The Martin P4M Mercator, although outwardly similar to the smaller Lockheed Neptune, was designed later and developed for a different requirement.
Nineteen of the much sleeker production machines were complete in Se.
The first flight was on September 20, 1946.
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 ).
Its specific 1946 design purpose was long-range patrol and mine laying.
The Martin P4M Mercator, although outwardly similar to the smaller Lockheed Neptune, was designed later and developed for a different requirement