Actually, per wiki, the USN had 13 squadrons that flew the F4D, and the USMC another 8, and over 400 were built. One USN F4D squadron was the only Navy squadron ever assigned to NORAD. Most F4D squadrons flew from carriers, as dedicated fighter interceptors. It was the first operational USN fighter to be supersonic in level flight, in addition to its superb climb performance for that time. The only real problem with the F4D was that avaiation technology was rapidly progressing at that time, and that the design was not multi role, like the types that would succeed it, such as the F8U Crusader and F4H Phantom.