What Do They Actually Spray on Planes to De-Ice Them?

09.01.2024 - 04:19 / afar.com / Delta Air Lines / Cooper

If you are boarding a plane in much of the United States during winter, chances are the aircraft will need to have a specially trained crew spray it with de-icing fluid before takeoff to remove ice and snow (or prevent more from sticking).

Even small amounts of snow, frost, or ice (or ice contaminants, in airline parlance), especially on the wings and tail, are dangerous for airplanes. For one, they add extra weight, which can make it challenging for pilots to do performance calculations, like how fast the plane can climb and if there’s enough runway to clear obstacles. They also interfere with air flow, which reduces lift and could block vents or impede sensors from operating correctly.

Simply put, de-icing allows travelers to fly the friendly skies safely during wintery conditions. Here’s everything you need to know about how and why airlines de-ice planes before takeoff.

De-icing happens most frequently from October to April each year, although according to Celley Buchanan, vice president of airport operations and customer service at Alaska Airlines, “De-icing can happen and be needed at any time of the year; it just depends on the temperature outside.”

Both Buchanan and Catherine Morrow, a senior communications coordinator at Delta Air Lines, said inspections are done on all aircraft when temperatures dip below 50 degrees, even briefly.

“For example, if the air is more humid and temperatures drop overnight, there could be an accumulation the next morning, even if the temperature warms up a bit,” Morrow said.

After each flight during colder months, the flight deck crew will inspect the plane for any ice contaminants, and if they find any, they’ll notify their de-icing crew, which may be staff or contract workers. It’s the responsibility of each airline, not each airport, to ensure all the planes across their network are properly prepared for takeoff, according to Perry Cooper, a media relations manager at Seattle–Tacoma International Airport.

An Alaska Airlines aircraft during an ice storm in Seattle in December 2022

Courtesy of Ingrid Barrentine/Alaska Airlines

If a plane does need de-icing, it will typically happen after all passengers and crew are onboard, and the plane is otherwise ready to take off. That’s because the solutions used to remove and prevent accumulation don’t have an infinite protection period, and time is of the essence.

“We use a term in the industry called holdover time, which is calculated by your flight deck crew, and they’ll use several different components, like the temperature outside and current weather conditions, to determine once an airplane is sprayed, how much time do you have to take off safely,” Buchanan said. Typically, she said, it’s about 22 minutes between