jet aircraft flying at 1000 km/h. With every complete rotation of the antenna, which takes 10 seconds, the aircraft will move 1000 km/h = 278 m/s * 10 = 2780 m, a little less than 3 km. On a display with a 300 km radius this represents a movement of only 0.5% across the display's face (600 km diameter), producing a tiny line segment between the two dots that is easy for an operator to interpret as an aircraft. But if the target speed is increased, its movement becomes more pronounced on the scope, making it less recognizable and more difficult to track. At Mach 3 (3500 km/h at 25,000 m) the same ten seconds of movement represent over 1.5% of the display's face. At this point, the slowly moving dot turns into a series of dim individual spots, which can more easily be mistaken for clutter. Additionally, since the spots are separated on the display, the returns no longer "add up," potentially reducing the returns to the same level as background noise, making it invisible. An operator seeing a line of small dots across their screen might eventually recognize the return as an aircraft. To frustrate even this, aircraft were designed to fly as high as possible. Assuming a high-speed aircraft flying at 90,000 feet, or 27 km, this means the aircraft will be above the maximum angle of the radar when it approaches within about of the station. Assuming it is first detected at , that means it is only visible over a range of . At Mach 3, this means it would be visible, even in theory, for about 3 minutes. This leaves very little time to arrange an interception. And thus the concept of using the blip/scan to avoid detection. A high-speed, high-altitude aircraft might fly over early warning radars without being recognized. Moreover, even if an operator recognized the blip as an aircraft, the small number of returns and fast movement across the display would make it difficult or impossible to manually calculate a trajectory for relay to intercepting aircraft. Aircraft projects Blip/scan spoofing was discovered during the late 1950s, a time when ground-controlled interception of manned interceptors was the only practical anti-bomber tactic. This led to a miniature arms race in itself, albeit a brief and abortive one. The Lockheed U-2 flew at high altitude but not at particularly high speed. Even before the