Which atmospheric condition can lead to the formation of ice on an aircraft?

The formation of ice on an aircraft is primarily associated with visible moisture at temperatures below 0 degrees Celsius. In these conditions, when the aircraft is flying through clouds, fog, or any other form of visible moisture, the supercooled water droplets can freeze upon contact with the aircraft's surfaces, resulting in ice accumulation. This scenario is particularly critical during flight, as ice can significantly affect aircraft performance, control, and safety.

In contrast, high air temperatures with low humidity and clear skies do not provide the necessary conditions for ice formation. Even at lower altitudes, if the air is dry (low humidity), the likelihood of moisture in the form of supercooled droplets is minimal, thus reducing the risk of icing. Similarly, low humidity at high altitudes may also prevent ice formation, as the availability of moisture is limited. Therefore, the presence of visible moisture combined with sub-zero temperatures is a key factor in ice hazard scenarios for aviation.