This F-4 was originally built for the USN as F4H-1 but, before delivery, modified to become the USAF YRF-110A Spectre prototype, which was redesignated RF-4C in 1962. In 1965, it became the YF-4E testbed, to test F-4E slats and Fly by Wire (as seen in this picture). In 1974, canards were added on this aircraft. This photo was taken after the unqiue Phantom was retired and preserved in the Air Force museum.