Airlines deice planes by spraying them with heated glycol-based fluids that melt and remove ice, then often add a thicker protective fluid that helps keep new ice from forming until takeoff. This process is tightly regulated and must be done right before departure so the aircraft’s critical surfaces stay clean and can safely generate lift.

Why planes need deicing

Even a thin layer of frost or ice on the wings or tail can seriously reduce lift and increase drag, which can be dangerous during takeoff. Ice can also break off in flight and hit engines or control surfaces, so regulations require that “critical surfaces” be free of frozen contamination before departure.

Step 1: Deicing (removing ice)

Deicing is the part you usually see from the window, with trucks and spray booms moving around the aircraft.

  • Ground crews use special trucks with extendable booms and nozzles to spray the plane just before departure.
  • They work in a set pattern, typically starting at the front of the fuselage, then wings, then tail surfaces, to ensure everything is covered.
  • The fluid is mostly water mixed with propylene or ethylene glycol, heated and sprayed at high pressure so it melts snow, frost, and ice.
  • These deicing fluids are relatively thin and are designed to remove existing contamination rather than stay on for long.

During spraying, the pilots usually switch off the cabin bleed air/ventilation so fumes do not circulate inside, though passengers may sometimes smell a sweet, maple-syrup-like odor that is considered safe at the exposure levels involved.

Step 2: Anti-icing (preventing new ice)

If it is still snowing, sleeting, or there is freezing drizzle, crews often do a second step called anti-icing.

  • Anti-ice fluids are similar glycol-based mixtures but thicker because they contain less water and added thickening agents.
  • They are applied cold in a uniform layer over wings and other critical surfaces to hold off new ice or snow while the aircraft taxis and lines up for takeoff.
  • Dyes (commonly green) are added so crews and pilots can see that the fluid is present and how it is flowing or fading.
  • As the plane accelerates on the runway, the thick anti-icing layer shears off and blows away, leaving clean surfaces for flight.

Regulators use the idea of “holdover time,” which is the window after treatment during which the fluids are expected to keep the aircraft protected; if that time expires due to delays or worsening weather, the plane must be treated again.

Fluids and safety considerations

The deicing and anti-icing fluids are carefully standardized into types, with different properties for different temperatures and operations.

  • Most commercial operations use propylene glycol mixtures because they are less toxic than traditional ethylene glycol, though both are effective at lowering freezing points.
  • Operators follow detailed FAA and industry guidelines about which fluid type to use, concentration, and method of application depending on precipitation and temperature.
  • Environmental impact is a concern, so airports often collect runoff in drainage systems for treatment rather than letting glycol-heavy water go directly into nearby waterways.

Inside, the crew checks performance data and ensures the aircraft stays within its holdover time; if not, they must return for another deice/anti-ice cycle before takeoff.

New and alternative technologies

Besides fluid spraying, there is ongoing work on more efficient or permanent solutions.

  • Some systems use electrically heated “tapes” or panels bonded to the skin; when powered, they generate heat and melt snow and ice on the surface.
  • Concept research looks at superhydrophobic coatings that shed water easily, combined with micro-reservoirs of antifreeze inspired by organisms like poison dart frogs.
  • These ideas aim to cut fluid use, lower costs, and reduce environmental impact while maintaining or improving safety margins.

Information gathered from public forums or data available on the internet and portrayed here.