During WWI, the North American P-51D Mustang is considered the pinnacle of American fighter aircraft. The aircraft's development drew on the specifications of the Royal Air Force and the addition of the Rolls Royce Merlin engine. The Mustang became a magnificent powerhouse of versatility and efficiency. Paired with its firepower and long-range capabilities, the Mustang asserted itself as a capable escort fighter. Following the conflicts of WWII, the Mustang saw use with Korea, as well as others until the 1980s.