four wing guns. Although these remanufactured Mustangs were intended for sale to South American and Asian nations through the MAP, they were delivered to the USAF with full USAF markings. They were, however, allocated new serial numbers (67-14862/14866, 67-22579/22582 and 72-1526/1541). The last U.S. military use of the F-51 was in 1968 when the U. S. Army employed a vintage F-51D (44-72990) as a chase aircraft for the Lockheed YAH-56 Cheyenne armed helicopter project. This aircraft was so successful that the Army ordered two F-51Ds from Cavalier in 1968 for use at Fort Rucker as chase planes. They were assigned the serials 68-15795 and 68-15796. These F-51s had wingtip fuel tanks and were unarmed. Following the end of the Cheyenne program, these two chase aircraft were used for other projects. One of them (68-15795) was fitted with a 106 mm recoilless rifle for evaluation of the weapon's value in attacking fortified ground targets. Cavalier Mustang 68-15796 survives at the Air Force Armament Museum, Eglin AFB, Florida, displayed indoors in World War II markings. The F-51 was adopted by many foreign air forces and continued to be an effective fighter into the mid-1980s with smaller air arms. The last Mustang ever downed in battle occurred during Operation Power Pack in the Dominican Republic in 1965, with the last aircraft finally being retired by the Dominican Air Force in 1984. Service with other air forces After World War II, the P-51 Mustang served in the air arms of more than 25 nations. During the war, a Mustang cost about $51,000, while many hundreds were sold postwar for the nominal price of one dollar to signatories of the Inter-American Treaty of Reciprocal Assistance, ratified in Rio de Janeiro in 1947. These countries used the P-51 Mustang: Australia In November 1944, 3 Squadron RAAF became the first Royal Australian Air Force unit to use Mustangs. At the time of its conversion from the P-40 to the Mustang, the squadron was based in Italy with the RAF's First Tactical Air Force. 3 Squadron was renumbered 4 Squadron after returning to Australia from Italy, and converted to P-51Ds. Several other Australian or Pacific-based squadrons converted to either CAC-built Mustangs or to imported P-51Ks from July 1945, having been equipped with P-40s or Boomerangs for wartime service; these units were: 76, 77, 82, 83, 84 and 86 Squadrons. Only 17 Mustangs reached the RAAF's First Tactical Air