When is the risk of icing on aircraft surfaces highest?

The risk of icing on aircraft surfaces is highest when the true outside temperature is between 0°C and -10°C. This temperature range is critical because it coincides with conditions that are favorable for icing to occur. When temperatures are around freezing, supercooled water droplets are often present in the atmosphere, particularly in clouds, and these droplets can freeze upon contact with the aircraft surfaces.

This temperature range is not only conducive to the formation of ice but also accounts for the atmospheric conditions in which moisture is abundant, such as during precipitation or in cloud cover. In contrast, at temperatures above 0°C, ice formation is much less likely, and below -10°C, while icing can still occur, the supercooled water droplets become less common.

The other options reference conditions that do not consistently correspond to the highest risk of icing. For example, stating that the risk is always present is too broad and does not reflect the reality of atmospheric conditions. High altitudes, such as above 20,000 feet, often have colder temperatures, but clear air at those elevations is less likely to contain the moisture necessary for icing. Lastly, limiting the risk to takeoff and landing ignores the potential for icing at cruising altitudes during flight, especially in