The P-51D Mustang is seen by many as one of the most iconic fighter aircraft in WWII. Clearing the German skies of Luftwaffe fighters, the P-51D was designed and built by the North American Aviation as commissioned by the Royal Air Force (RAF) in the 1940s. The P-51B variant was designated as the Mustang III during its service in the RAF. This version had the modified coolant radiator which increased the plane's maximum speed by 50mph. The Mustang III had one design flaw: its low-profile canopy. Because of its limited headroom, even short pilots were forced to press their heads against the top of the canopy to improve visibility. As a result, the RAF had the old canopy replaced with clear, sliding ones. This new canopy was designed by Robert Malcolm, and was therefore called the "Malcolm hood." The same canopy design can be seen in the U.S. Navy's version of the Corsair, the F4U-1D.