How does one identify a Class D airspace on a chart?

A Class D airspace is identified on aeronautical charts by a blue segmented circle. This visual representation indicates the lateral boundaries of the controlled airspace around an airport that has an operational control tower. The blue color signifies the presence of controlled airspace, while the segmented nature of the circle indicates that it is not fully enclosed, distinguishing it from other classes of airspace.

This identification method allows pilots to readily recognize the airspace they are entering or flying in, ensuring they adhere to any communication and operational requirements associated with flying in Class D airspace, which typically includes establishing two-way radio communication with the control tower. Understanding the visual markers on aeronautical charts is crucial for safe navigation and compliance with airspace rules.