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Class D (blue cylinder) airspace starts at the surface of an airport with an operating control tower. It extends vertically to approximately 2,500' feet above the airport elevation. Chico airport (Figure 1), has an elevation of 238' MSL. This makes the top of the Class D airspace approximately 2,700' MSL ([27]). The radius of Class D airspace is approximately 4.3 nautical miles (but this varies from airport to airport). Figure 2 shows a sectional chart excerpt of Chico's Class D airspace. 
Rod Machado
Rod Machado is a flight instructor, author, educator, and speaker.
