achieve controlled supersonic flight. Operational history Amongst RCAF pilots, the Canuck was affectionately known as the "Clunk", the name has been attributed to the noise produced by the forward landing gear during retraction into its well after takeoff. Another common, less attractive, nickname was the "Lead Sled", a reference to its heavy controls and general lack of maneuverability, a nickname that was shared with a number of other 1950s aircraft. Others included CF-Zero, the Zilch, and the Beast, all references to an aircraft many pilots considered less glamorous than RCAF day fighters like the Canadair Sabre. Operationally, many CF-100s functioned under the US–Canadian North American Air Defense Command (NORAD), which protected North American airspace from Soviet intruders, particularly the threat posed by nuclear-armed bombers. Additionally, between 1956 and 1962, as part of the North Atlantic Treaty Organization (NATO), four CF-100 squadrons were based in Europe with 1 Air Division; for some time, the CF-100 was the only NATO fighter that was capable of operating in zero visibility and poor weather conditions. Around the start of the Korean War in the early 1950s, the United States Air Force (USAF) found itself in urgent need of a jet-propelled, all-weather, interdiction/surveillance aircraft. This urgency was so great that the USAF was willing to consider two foreign designs: the CF-100 and the English Electric Canberra. Following an evaluation, the CF-100 was rejected due to its insufficient range and payload capabilities; the rival English Electric design was selected and developed into the Martin B-57 Canberra. At its peak, the CF-100 served with nine RCAF squadrons in the mid-1950s. Four of these squadrons were deployed to Europe under the NIMBLE BAT ferry program, replacing multiple NATO RCAF squadrons equipped with Canadair Sabre day fighters to provide all-weather defense against Soviet intruders. While flown in the North American theatre, the CF-100 would typically retain a natural metal finish; however, those flying overseas were given a British-style disruptive camouflage scheme: dark sea gray and green on top, light sea gray on the bottom. During his Avro Canada years, the Chief Development Pilot, S/L Żurakowski, continued to fly as an aerobatic display pilot, with spectacular results, especially at the 1955 Farnborough Airshow where he displayed the CF-100 in a "falling-leaf." He was acclaimed again as the "Great Żura" by many aviation and industry observers who could not believe a large, all-weather fighter could be put through its paces so