The PHM program was started in the early 1970s. The aim was to withdraw frigates and destroyers from guarding coastal waters and to replace them with inexpensive, powerful hydrofoil boats. In addition to the US Navy, the German Navy , the Royal Navy , the Royal Canadian Navy and the Marina Militare were involved in the project. It was planned to build up to 100 ships, but for cost reasons only the USS Pegasus , then called Delphinius , was built. A few years later another five boats were created, but the participating NATO - naval forces had lost interest. Only the Italian Navy maintained seven boats of a similar type ( Sparviero class ) until the early 1990s .