How do de-icing and anti-icing differ and when is each used?

• A. De-icing removes existing ice; anti-icing prevents ice formation; used per weather and procedures.
• B. Anti-icing removes existing ice; de-icing is unrelated.
• C. De-icing removes ice only; anti-icing is unrelated.
• D. De-icing and anti-icing are interchangeable.

Answer: (B)

De-icing and anti-icing address ice on aircraft in two distinct ways: removal versus prevention. De-icing is used to remove ice that has already accumulated on surfaces; it uses fluids that melt or loosen ice and may involve manual or mechanical cleaning until the surface is clear. Anti-icing is applied before flight to prevent ice from forming in icing conditions, creating a protective layer that slows or delays ice buildup and establishes a holdover time. In practice, you de-ice when you already see ice or frost on the aircraft; if icing conditions are expected to continue, you apply anti-ice beforehand to keep surfaces clear during the period before takeoff. They are not interchangeable—one is for removing existing ice, the other for preventing it from forming.