Prevailing visibility is defined as what?

• A. The maximum visibility observed at any point.
• B. The longest distance at which an object can be seen in any direction.
• C. The greatest horizontal visibility equaled or exceeded throughout at least half the horizon circle.
• D. Visibility measured by a single observer.

Answer: (C)

Prevailing visibility is a broad, representative measure of how far you can see in the open air around you. It’s defined by the greatest horizontal distance that can be seen and identified in at least half of the horizon circle around the observer. In other words, you should be able to see objects at that distance in at least half the directions, not just in one lucky direction. This makes it a useful, overall value for flight planning and weather reports because it reflects the general visibility conditions rather than a sighting that only exists in a single direction. It’s not the maximum you can see in any single direction, it’s not the farthest distance seen in one line of sight, and it’s not tied to a single observer’s measurement.