Why is the freezing level important when planning to avoid icing?

• A. Icing is most likely where visible moisture exists below the freezing level; knowing the freezing level helps plan altitude to minimize icing risk
• B. Icing occurs only above the freezing level
• C. Freezing level has no impact on icing risk
• D. Icing is guaranteed below the freezing level

Answer: (D)

The freezing level marks the altitude where the air temperature is 0°C. Icing happens when there is visible moisture in subfreezing air, so icing risk is greatest in clouds or moisture below that level. Knowing where the freezing level lies helps you choose altitudes that avoid flying through moist, subfreezing layers, or to plan to be above them, thereby reducing icing risk. It’s not guaranteed that icing will occur below that level, and icing can occur in other conditions as well, but this rule of thumb explains why the freezing level is a key planning factor.