North American F-51H Mustang

Differences between a P51-D (top) 

and a P-51H (bottom)

The Mustang was among the best and most well-known fighters used by the U.S. Army Air Forces (USAAF) during World War II. Possessing excellent range and maneuverability, the P-51 operated primarily as a long-range escort fighter and also as a ground attack fighter-bomber. The Mustang served in nearly every combat zone during WWII and later fought in the Korean War.

North American eventually developed a considerably lightened Mustang, which became the P-51H. The P-51H (NA-126) was the final production Mustang, embodying the experience gained in the development of the XP-51F and XP-51G aircraft. This aircraft, with minor differences as the NA-129, came too late to participate in World War II, but it brought the development of the Mustang to a peak as one of the fastest production piston-engine fighters to see service.[53]

The P-51H used the new V-1650-9 engine, a version of the Merlin that included Simmons automatic supercharger boost control with water injection, allowing War Emergency Power as high as 2,218 hp (1,500 kW). Differences between the P-51D included lengthening the fuselage and increasing the height of the tailfin, which reduced the tendency to yaw. Service access to the guns and ammunition was also improved. The canopy resembled the P-51D style, over a raised pilot's position, and the aircraft was given a new propeller with wider, uncuffed blades and rounded tips to allow the additional power to be better used.

Although some P-51Hs were issued to operational units, none saw combat in World War II and, in postwar service, most were issued to reserve units. One aircraft was provided to the RAF for testing and evaluation. Serial number 44-64192 was designated BuNo 09064 and used by the U.S. Navy to test transonic airfoil designs and then returned to the Air National Guard in 1952. The P-51H was not used for combat in the Korean War despite its improved handling characteristics, since the P-51D was available in much larger numbers and was a proven commodity.

Many of the aerodynamic advances of the P-51 (including the laminar flow wing) were carried over to North American's next generation of jet-powered fighters, the Navy FJ-1 Fury and Air Force F-86 Sabre.

In mid 1944, the Bureau of Aeronautics asked North American to submit a proposal for a navalized P-51 Mustang. The resulting NAA-133 was based on its P-51H and to be powered by a Merlin V-1650-11 engine.