How are the boundaries of Class D airspace defined on aeronautical charts?

Class D airspace is depicted on aeronautical charts with solid blue lines. This representation is consistent across various types of sectional charts, approach charts, and other aviation charts. The solid blue line clearly indicates the lateral boundaries of Class D airspace, which generally extends from the surface up to a specified upper limit, often 2,500 feet above the airport elevation.

Using solid blue lines helps pilots easily identify and separate Class D airspace from adjacent classifications, such as Class C, which is shown with a solid magenta line. Recognizing these visual markers is crucial for pilots to ensure compliance with airspace regulations and to maintain situational awareness when operating in and around controlled airspaces.

The other options mentioned, such as dashed red lines, shaded green areas, and dotted yellow circles, represent different types of airspace or navigational features and are not used to define the boundaries of Class D airspace on aeronautical charts.