What does "D" signify on an airport diagram?

On an airport diagram, "D" typically signifies a deicing area. Deicing areas are specifically designated locations on an airport where aircraft are treated to remove ice or snow from their surfaces before departure. This process is crucial for ensuring the safety and efficiency of aircraft operations, particularly in winter conditions or during inclement weather.

Understanding the context of various symbols on airport diagrams is essential for pilots and ground personnel to navigate effectively around the airport. While the other options could be relevant in certain operational contexts, the specific designation of "D" for deicing areas is a standardized practice commonly recognized in aviation charts. This helps maintain clarity and safety in airport operations, especially during seasons when deicing is frequently required.