What is the most commonly used type of visibility?

The most commonly used type of visibility in aviation is prevailing visibility. This term refers to the maximum distance at which objects can be seen and identified within a specific area. It is particularly significant for pilots because it provides critical information regarding the ability to navigate and land safely under various weather conditions.

Prevailing visibility is often used during flight operations, as it reflects the visibility conditions most often encountered in a given location, taking into account the range of visibility upon observation from the airfield. Flight operations, weather reporting, and air traffic control heavily rely on this metric to ensure that pilots are adequately informed about potentially hazardous visibility conditions.

In contrast, the other types of visibility—runway visibility, horizontal visibility, and vertical visibility—serve more specific purposes. Runway visibility is relevant only to a particular runway's operational factors, while horizontal visibility generally refers to the distance at which objects can be seen in a horizontal plane. Vertical visibility pertains to the distance that one can see upward into the sky, which is typically assessed in situations where the obscuration of the horizon occurs, such as during fog or heavy precipitation. However, prevailing visibility encapsulates the overall conditions that pilots most frequently work with, making it a crucial aspect of flight safety.