The Martin P6M SeaMaster, built by the Glenn L. Martin Company, was a 1950s strategic bomber flying boat for the United States Navy that almost entered service; production aircraft were built and Navy crews were undergoing operational conversion, with a service entry about six months off, when the program was cancelled on 21 August 1959. Envisioned as a way to give the Navy a strategic nuclear force, the SeaMaster was eclipsed by the Polaris submarine-launched ballistic missile.