What is the most common cause of low visibility during aviation operations?

Low visibility during aviation operations is most commonly caused by fog and heavy precipitation. Fog occurs when moisture in the air condenses into tiny water droplets, creating a thick mist that can severely limit visibility. This phenomenon is particularly problematic for pilots during takeoff, landing, and navigation, as it obscures ground references and can lead to increased chances of accidents if proper precautions are not taken.

Heavy precipitation, such as rain or snow, also contributes significantly to reduced visibility. Rain can create a blurred vision effect as it distorts light, while snow can accumulate on surfaces and further obscure visibility. Both conditions can make it challenging for pilots to see the runway, other aircraft, and critical navigational aids.

In contrast, high altitudes generally do not directly contribute to low visibility; rather, they are often associated with clearer air layers above weather systems. Clear skies typically indicate good visibility conditions, and air traffic congestion does not influence weather conditions that would cause low visibility. Thus, fog and heavy precipitation are the primary culprits behind low visibility in aviation settings.