Which statement best describes the necessary condition for icing to occur in flight?

• A. Visible moisture must be present
• B. Only very high altitude with no moisture allows icing
• C. Icing occurs with dry air and low humidity
• D. Icing occurs only after takeoff in clear weather

Answer: (A)

Icing in flight occurs only when there are liquid water droplets in the air that can strike the aircraft surface and freeze. The essential condition is visible moisture—such as clouds, fog, drizzle, or rain—that provides those droplets. Without moisture, even if it’s cold, ice cannot form because there’s nothing to freeze onto the airplane. Dry air or clear weather has no droplets to create ice, and icing is not limited to after takeoff in clear weather. So, the presence of visible moisture is the necessary condition for icing to occur.