How do pilots determine what class of airspace they are entering?

The correct answer is found in the approach pilots take to identify airspace classifications. Referring to sectional charts is essential for pilots as these charts provide detailed visual representations of airspace structures, including the boundaries and classifications of the different types of airspace. Sectional charts show the altitudes, requirements, and other pertinent information necessary for safe navigation and compliance with airspace regulations.

Using GPS devices can enhance situational awareness and may assist in navigation, but they do not provide the detailed visual information about airspace classifications that sectional charts do. While communication with Air Traffic Control is vital for managing traffic and receiving updates, it is primarily a supportive tool rather than the primary method for determining airspace classifications. Estimating based on flight altitude does not accurately reflect airspace boundaries, as these are defined by geographic locations rather than merely altitude. Therefore, the most reliable and effective method is by utilizing sectional charts.