If you’ve flown much during the colder months, odds are you’ve been on a flight that had to be deiced before takeoff. Airplanes, especially jets, fly at very high altitudes and very fast speeds. At 35,000 feet, it’s not uncommon to see temperatures dip below negative sixty degrees Fahrenheit. If planes can operate in these extreme subzero temperatures regularly, why is it necessary to deice when on the ground?
The reason for deicing lies within the design of the aircraft itself. All airplane designs are very precisely engineered to be flown as they were built, without the addition of any contamination. No, this doesn’t mean the aircraft can’t become ill with a virus. In aviation, the term contamination often refers to the buildup of ice on the aircraft’s wings and fuselage (the body of the aircraft). Even a small amount of ice on the wings changes the wing’s shape and impacts its aerodynamics. But fear not! As with everything in aviation, there are numerous precautions and procedures for all commercial flights to ensure safe operations in and around icing conditions.
The process of deicing is relatively simple, but there’s a bit more to it than meets the eye. There are primarily two types of deicing fluid that are used in the United States. Both fluids are glycol based but have their differences. The first type, which is orange, is a true deicer. It’s the most diluted form of deicing fluid and is used to remove snow and ice from an aircraft. The other fluid is thicker and designed to stick to the aircraft for a defined period of time, making it more of an anti-ice fluid. Each fluid is applied hot, which is why you see so much steam when deicing in colder temperatures. Your pilot will tell the ground crew exactly what type of deicing fluid they need and where. In many conditions, they’ll just request deicing of the wings and tail.
In conditions where there is no freezing precipitation, you’ll get a spray of of the deicer and be on your way. If it’s snowing, your flight will first get a coat of deicer, followed up with the anti-ice fluid. Based on the temperature and weather conditions, pilots know exactly how long they have to take off after being deiced. If they exceed this hold time, they must return to the gate to be deiced again. Additionally, pilots always visually inspect the wings before taking off in snowy conditions, regardless of how long ago the aircraft was deiced. During takeoff, the deicing fluid blows off the wings as the aircraft gains speed.
Once airborne, aircraft are able to use their own anti-ice and deicing systems. Most jets use hot air from the core of the engine to heat metal surfaces along the edges of the wings to prevent and remove ice.
That said, pilots and Air Traffic Control do all they can to avoid substantial icing conditions. It’s rare to ever spend a substantial amount of any given flight in icing conditions. At high altitudes, air is often so dry that there’s not enough moisture to generate any significant form of icing on the aircraft. Like all phases of flight, aircraft manufacturers, airlines and pilots have handling ice down to a science. Rest assured that if the winter weather is beyond the parameters for safe flight, your flight won’t leave the gate.