In 1930s, The Martin PBM-3 Mariner was designed as a Patrol Bomber Flying Boat for the US Navy. Originally, this flying boat was known as the Martin 162. The first prototype - the quarter-scale 162A - flew in 1937. The full-scale prototype - the XPBM-1 - first flew in February 1939. There were 1,285 built. The type entering service was in September 1940.
The PBM-3 Mariner is a huge flying boat with a very graceful, bird-like silhouette. It is designed for very long range operations. The craft is equipped to remain away from its base for protracted periods while fulfilling its duties as a patrol bomber, convoy escort or fleet operations scout. Its capability to fly very long range mission is underscored by it having a galley and sleeping accommodations.
The Mariner was built to replace the older Consolidated PBY series, but so many patrol planes were needed, that it ended up as an addition and not a replacement. Over 1,000 Mariners were built during the war. They proved so useful and reliable that many remained in service for decades. The PBM-3 was similar to the PBM-1 in most respects, differing mainly in fit of uprated P&W R-2600-12 engines with 1,270 kW (1,700 HP) each; larger and fixed wing floats; and revised engine nacelles that featured much bigger bombbays.
Only 32 PBM-3s as such were built and never saw formal service in their original configuration. 31 of them were converted to a transport configuration, the ""PBM-3R"", and 18 new-build PBM-3Rs were constructed as well. These machines had armor and armament removed, with the turrets faired over; a reinforced floor, cargo doors, and a hoist; and removeable seating for 20 passengers, though it was nothing unusual for them to carry 33 or more.