What is the definition of visibility in aviation?

In aviation, visibility is defined as the greatest horizontal distance at which prominent objects can be seen and identified. This is crucial for safety during flight operations, as it influences a pilot's ability to navigate, avoid obstacles, and ensure safe landing and takeoff. Visibility conditions can vary due to weather phenomena such as fog, rain, or haze, significantly impacting flight safety.

The other options do not correctly define visibility in aviation. For instance, distance before refueling refers to operational limits rather than visual perception, maximum altitude pertains to altitude restrictions rather than visibility, and the area required for takeoff and landing relates to physical space rather than the ability to see. Visibility is fundamentally about how far one can see horizontally, which is why this option is the correct definition.