What is a key guideline for adding designators to runway numbers?

Using letters L and R for left and right of the approaching pilot is the key guideline for adding designators to runway numbers. This practice ensures clarity and safety for pilots during approach and landing, particularly when they are dealing with parallel runways. By designating one runway as "Left" and another as "Right," it becomes easier for pilots to distinguish between runways, reducing the potential for confusion and enhancing situational awareness.

When multiple runways are aligned parallel to each other, this method directly relates to the pilot's perspective as they approach the airfield, making it a standardized practice in aviation communication. This guideline reflects the importance of clear and unambiguous instructions in maintaining safe flight operations, especially in busy air traffic environments.

The other options do not align as effectively with the established principles for runway designators. For instance, using letters A and B might seem intuitive, but it does not account for the perspective of the approaching pilot. Meanwhile, adding numbers to indicate elevation or designating based on the nearest airport location does not provide the necessary clarity that pilots need when navigating multiple runways.