History
The P6M SeaMaster emerged from the US Navy’s ambition in the early 1950s to develop its own nuclear-capable aircraft. This initiative followed the cancellation of the USS United States program in favor of the Air Force’s B-36 bomber. As a result, the Navy introduced the Seaplane Striking Force, intending to field a flying boat that could carry nuclear weapons and operate independently from the sea.
In April 1951, the Navy issued requirements for a flying boat with a 30,000-pound payload, a range of over 1,500 miles, long-range minelaying and reconnaissance capabilities, and a secondary nuclear strike function. One key goal was to mine the waters around Soviet submarine bases, denying access to the open sea and preventing returning submarines from docking. The aircraft also needed to achieve 0.9 Mach at low altitudes to avoid radar detection.
By July 1951, the Navy invited 12 manufacturers to submit proposals. Martin and Convair stood out as top contenders, with the Navy ultimately selecting Martin’s design. Known as the Model 275, this concept became the XP6M-1 prototype. The SeaMaster featured a sleek, all-metal hull with wings swept at 40 degrees, a high-mounted T-tail, and stabilizing floats at the wingtips. To mitigate water spray during takeoff, four turbojet engines were mounted in pairs above the wings. The aircraft also featured a rotating bomb bay designed to remain watertight and housed a remote-controlled tail turret armed with two 20-mm cannons. A five-man crew would operate the aircraft, which consisted of the pilot, co-pilot, navigator-minelayer, radio operator, and gunner.
The first prototype was constructed in Baltimore and made its maiden flight over Chesapeake Bay on July 14, 1955. It was powered by four Allison J71-A-4 engines. However, the close placement of the engines caused heat damage to the fuselage, prompting modifications to the second prototype. Tragically, the program suffered mishaps: on December 7, 1955, the first prototype got a control system failure and disintegrated midair, killing the entire crew, and on November 9, 1956, the second prototype crashed due to a malfunctioning elevator jack. The crew of the second prototype ejected safely and survived.
Despite these setbacks, Martin continued refining the SeaMaster. In January 1958, the first pre-production YP6M-1 unit was completed, with five more built that year. These aircraft underwent trials for bombing, minelaying, and reconnaissance missions, but ongoing issues with the engines and flight controls led to the cancellation of the P6M-1 variant. In response, Martin developed the improved P6M-2 model.
The P6M-2 was equipped with more powerful Pratt & Whitney J75 engines, an aerial refueling probe, advanced avionics, and a redesigned canopy for better pilot visibility. The increased weight allowed the aircraft to maintain lower hover altitudes over water, removing the need for wing anhedral. With a top speed of Mach 0.9, the P6M-2 exceeded the performance of the Air Force’s B-52 Stratofortress. By mid-1959, three P6M-2s had been delivered to North Carolina for operational evaluation, where crews trained for mine-laying missions.
However, the introduction of ballistic missile submarines rendered the SeaMaster program unnecessary. Submarines offered a more efficient and reliable platform for nuclear strikes and minelaying, leading the Navy to cancel the P6M program in August 1959. Budget constraints, technical delays, and competition with aircraft carriers for funding further sealed its fate.
In total, eight P6M-2 units were built, although only three ever flew. Martin attempted to repurpose the design as a civilian airliner, the “SeaMistress,” but the proposal failed to gain support. This disappointment marked the end of Martin’s involvement in aircraft production, as the company pivoted toward missiles and electronic systems. All remaining SeaMasters were scrapped, though parts of the aircraft–such as two tail sections, a fuselage fragment, and wing floats–are preserved at the Glenn L. Martin Aviation Museum in Baltimore.
When the program concluded, the 12 SeaMasters had accumulated a total of 536 flight hours. The P6M SeaMaster was the last flying boat developed for the US military. Its predecessor, the P5M Marlin, remained in service until November 1967 before being replaced by the land-based P-3 Orion, marking the end of the Navy’s use of flying boats.
