Skip to content

How aircraft deal with the dangers of snow and ice

Jan. 29, 2022
12 min read
This post contains references to products from one or more of our advertisers. We may receive compensation when you click on links to those products. Terms apply to the offers listed on this page. For an explanation of our Advertising Policy, visit this page.

Editor’s note: This post has been updated with new information.


As a major winter storms puts the Northeastern in its sights, we're taking a closer look at how pilots and planes deal with snow.

As winter takes hold, snow and ice become a regular part of aviation. While it may look great in your Instagram photos, icy conditions can cause some serious headaches for airlines and airports -- and here's why.

For more TPG news delivered each morning to your inbox, sign up for our daily newsletter.

Why ice and aviation don’t mix

Aircraft fly not because of the engines, but because of the lift generated by the wings. The engines merely provide the forward propulsion to create that lift. As the aircraft accelerates down the runway, the airflow over the wing increases. When this airflow reaches a critical point, enough lift is generated by the wings to enable the aircraft to leave the ground and start climbing up into the air.

For every takeoff, we calculate the exact engine power and speeds required to lift off safely. When we hit the takeoff speed, known as Vr, we pull back on the stick and the aircraft eases into the air. However, these speeds are based on a “clean wing,” one free from any contamination from snow or ice.

The design of the wing on an aircraft doesn’t come together by accident. Millions of man-hours are dedicated to creating the perfect angle and shape, to facilitate the ideal amount of lift as the air flows over the smooth surfaces.

(Photo by Getty/Andrew Burton)

If there is snow or ice on the wing, the air will not flow smoothly and can break away from the surface. This results in a lack of lift. Therefore, for a speed that we have calculated will provide enough lift to take off, there will actually be less lift being generated. More speed will then be required to reach this critical speed, something which there may not be enough runway remaining to achieve.

In addition to contaminated wings, ice and snow can also cause problems with the external sensors of the aircraft.

Sign up for our daily newsletter

In order to ascertain the speed, altitude and a whole host of other parameters, there are a number of sensors and probes outside the aircraft. Of these, the pitot tubes are one of the most important.

Facing into the oncoming airflow, they measure how fast the aircraft is traveling through the air, giving the pilots important information about the aircraft’s speed. If these probes become blocked with ice and snow, they will give incorrect readings, causing problems in the flight deck. As a result, it’s important to ensure that they are clear before departure.

As a result, pilots take ice and snow contamination on the aircraft very seriously.

Before takeoff

With the knowledge that ice and snow are bad for aviation, there are a number of steps we take to ensure that the aircraft is safe for departure.

If there’s been a massive dumping of snow or it’s currently snowing, getting de-iced is a no-brainer. However, sometimes if there has been a frost overnight it can be a little difficult to tell whether it’s ice on the wing or just condensation.

Even before reporting for duty, our minds are always thinking several steps ahead. If it’s early morning and you’ve had to scrape ice off the car before driving into work, there’s a fair chance that the aircraft will also be covered in ice.

Checking the aircraft for ice and snow is an important part of the exterior safety check. (Photo by Getty/yoh4nn)

Arriving at the aircraft, we will often get a good view of the airframe as we climb up the steps or walk down the jetty. If the view isn’t great, a look out of the cabin windows will often give us more information as to the state of the wing.

Finally, before every flight one of the pilots carries out an external safety check, including the state of the wings and fuselage. On smaller aircraft, reaching the wing isn’t too much of a problem. However, on larger aircraft like the 787 Dreamliner which I fly, the wing is a little bit out of reach.

If we are still not sure of whether it’s ice or condensation on the wing surface, engineers can use a special lift to reach the wing and inspect it much more closely. If there is any doubt at all, we will always take the safest option and get the wings de-iced.

So what exactly does the de-icing process actually involve?

A two-stage process

The de-icing process is normally a two-stage process. First, the ice and snow deposits must be removed from the aircraft — this is the de-icing process. Then the wings and tail need to be protected from further contamination before the aircraft gets airborne — the anti-icing process.

De-icing

To remove the ice and snow deposits, the aircraft is sprayed with a hot mixture of glycol and water. This literally blasts the icy deposits off the wing. Once this is done, theoretically the aircraft is good to go. However, if the temperature is close to or below freezing and there is still moisture around in the form of fog or falling precipitation, there’s always a chance that more could settle on the wings before takeoff. To stop this from happening, the anti-icing stage is carried out.

Related: Low visibility: How aircraft operate in foggy conditions

De-icing an Airbus A320. The fluid is a mixture of hot glycol and water. (Photo by Thomas Cooper/Getty Images)

Anti-icing

Anti-icing fluids are similar to de-icing fluids except that they also contain polymeric thickeners. This results in a layer of what often looks like green or yellow slime on the surface of the wings, preventing any falling precipitation from settling. While this is effective at the time of spraying, it’s only good for so long. Depending on what type of anti-icing fluid was used and the current weather conditions, the anti-icing may be effective for anything up to a couple of hours down to only a couple of minutes. This is known as the holdover time. Once this time has expired, the pilots cannot be sure that the wings are clear from snow and ice and the whole process must start again.

On-stand treatment

At airports where the winters aren’t particularly severe, de-icing is normally done on the gate. This involves one or sometimes two specially designed trucks arriving at the aircraft side. Once the doors are closed and the air bridge is detached, they then begin spraying the aircraft. Depending on the level of contaminant and the expertise of the de-icing crew, this can take anything from around five minutes to 30 minutes. As soon as the anti-icing treatment begins, the clock is ticking on the holdover time.

Remote treatment

For larger airports where cold weather operations are a regular occurrence, they will often have specialized remote de-icing areas, normally close to the runway. Aircraft push back and start their engines as normal and then taxi out toward the remote de-icing area. If you’re on a flight where you seem to be taxiing to the runway with the wings covered in snow, do not worry. You will be heading toward one of these remote de-icing areas. Once in place with the parking brake set, the de-icing vehicles begin spraying the aircraft. They key difference here is that the engines remain running whilst the process is carried out. The main advantage here is that once the treatment has been completed, the aircraft only has to taxi a short distance to the runway and can be airborne in a matter of minutes. This is ideal when the holdover time may only be very short.

On the aircraft

Once airborne, while snow won’t settle on the aircraft, the build-up of ice can be a problem. As the aircraft flies through visible moisture such as clouds and fog, if the temperature is low enough ice can start to form in the engines and on the leading edge of the wings. In order to counter this, aircraft have a number of systems to stop this accumulation of ice.

Automatic ice detection system

Aircraft such as the Boeing 787 Dreamliner have an automatic ice detection system that senses the existence of icing conditions and provides signals to automatically control the various anti-ice systems on board. The system has two detectors that measure atmospheric liquid water content and use a variety of temperature sources to determine if icing conditions exist.

The wings

Depending on the aircraft type, there are a number of different defenses against the build-up of ice on the leading edge of the wing.

Most aircraft use hot air from the engine, known as bleed air. This is fed along ducts in the leading edge, warming it up and melting the ice off. Whilst this is an efficient way of getting rid of the ice, the bleed air saps power from the engine and also causes greater drag as it exits the wing into the atmosphere. Both of these factors require greater fuel burn to make up for the loss of power and aerodynamic efficiency.

Modern jets, like the 787 Dreamliner, have taken a different approach to wing anti-icing. The 787 uses a series of electrically heated blankets that are bonded to the inside of the leading edge structure. The heating of these blankets is enough to melt any ice forming on the wing. This system is far more effective, using around half the power that a traditional bleed system would use.

In addition, because there are no bleed air exhaust holes, drag over the wing and generated noise is reduced, making the Dreamliner not only more fuel-efficient but also quieter.

The engines

While the exhaust of the engine is pretty hot, as the pressure changes at the front of the engine, the temperature can drop and ice can start to build up. This normally happens with air temperatures of between 10 and -40 degrees Celsius.

To stop this from happening, bleed air is used to raise the temperature. When icing conditions exist, the engine anti-ice valves open and hot bleed air is fed into the engine inlet and core, stopping ice from forming. When the aircraft exits the icing conditions, the valve closes automatically.

By having the system operational only when needed, it reduces the extra fuel burn as explained above.

Remote de-icing a 787 Dreamliner. (Photo by author)

Windows

Like on your car, the flight deck windows can also get iced up. Not great when you’re trying to drive to work, even worse when you’re trying to land an aircraft with 240 people on board. To counter ice on the windshield, the glass itself is electrically heated.

The outer surface has anti-icing and the inner surface has anti-fogging protection. These systems operate at all times, whether on the ground or in the air.

Air conditioning inlets

Unlike most aircraft, the air that you breathe in the cabin of a 787 comes directly from the outside. Whilst this is great for your health and well-being, it means that the inlets are also prone to ice build up, just like the leading edges of the wings.

To stop these inlets from icing up, there is an electric heater on the leading edge of each inlet. This also reduces ice formation further down the air conditioning ducts.

Probes

As mentioned above, there are a number of probes and sensors outside the aircraft which are critical to sensing the airspeed, altitude and temperatures to be displayed in the flight deck. To stop these from succumbing to ice, they are electrically heated when the engines are running.

Bottom line

Pilots are well aware of the threat that snow and ice pose to the safe conduct of their flight. Before getting airborne, we will always ensure that the aircraft is clear from all snow and ice. Once in the air, ice is still a threat but aircraft have a number of systems that protect against critical parts icing up. De-icing often brings delays to those airports where cold weather isn’t a regular occurrence but those airports which do suffer long, cold winters tend to be well prepared for mass de-icing. Even though it may be frustrating to deal with delays that de-icing causes, your pilots will never take a risk with your safety. If in doubt, de-ice.

Featured image by Getty Images
Editorial disclaimer: Opinions expressed here are the author’s alone, not those of any bank, credit card issuer, airline or hotel chain, and have not been reviewed, approved or otherwise endorsed by any of these entities.

Top offers from our partners

How we chose these cards

Our points-obsessed staff uses a plethora of credit cards on a daily basis. If anyone on our team wouldn’t recommend it to a friend or a family member, we wouldn’t recommend it on The Points Guy either. Our opinions are our own, and have not been reviewed, approved, or endorsed by our advertising partners.
See all best card offers

TPG featured card

Best card for premium perks while traveling
TPG Editor‘s Rating
Card Rating is based on the opinion of TPG‘s editors and is not influenced by the card issuer.
4 / 5
Go to review

Rewards

2 - 10X points
10XEarn unlimited 10X miles on hotels and rental cars booked through Capital One Travel
5X5X miles on flights booked through Capital One Travel.
2X2 Miles per dollar on every purchase, every day

Intro offer

75,000 bonus miles
Earn 75,000 bonus miles when you spend $4,000 on purchases in the first 3 months from account opening, equal to $750 in travel

Annual Fee

$395

Recommended Credit

740-850
Excellent
Credit ranges are a variation of FICO© Score 8, one of many types of credit scores lenders may use when considering your credit card application.

Why We Chose It

The Capital One Venture X card is one of the best all-round travel credit cards ever launched. Not only is it offering a tremendous welcome bonus, but cardholders can earn tons of miles on everyday spending and receive a 10,000-mile anniversary bonus to boot. Its annual fee is $395, but cardholders can count on up to $300 in statement credits toward travel booked through Capital One Travel each year and other valuable benefits like access to Priority Pass lounges and Capital One’s own growing family of airport lounges.

Pros

  • Excellent welcome offer worth 75,000 miles after you spend $4,000 on purchases in the first three months.
  • Up to $300 in annual travel statement credits toward bookings make through Capital One Travel.
  • 10,000 bonus miles (worth $100 toward travel) each account anniversary.

Cons

  • The $395 annual fee might be expensive for some, but this card’s benefits provide much more value than that.
  • If you don’t travel frequently, this might not be the best card for you.
  • Earn 75,000 bonus miles when you spend $4,000 on purchases in the first 3 months from account opening, equal to $750 in travel
  • Receive up to $300 back annually as statement credits for bookings through Capital One Travel, where you'll get Capital One's best prices on thousands of options
  • Get 10,000 bonus miles (equal to $100 towards travel) every year, starting on your first anniversary
  • Earn unlimited 10X miles on hotels and rental cars booked through Capital One Travel and 5X miles on flights booked through Capital One Travel
  • Earn unlimited 2X miles on all other purchases
  • Unlimited complimentary access for you and two guests to 1,400+ lounges, including Capital One Lounges and our Partner Lounge Network
  • Receive up to a $100 credit for Global Entry or TSA PreCheck®
  • Use your Venture X miles to easily cover travel expenses, including flights, hotels, rental cars and more—you can even transfer your miles to your choice of 15+ travel loyalty programs
  • Named editors' choice for "Best New Credit Card of 2021" by The Points Guy
  • Earn 10 miles per dollar when you book on Turo, the world's largest car sharing marketplace, through May 16, 2023
Best card for premium perks while traveling
TPG Editor‘s Rating
Card Rating is based on the opinion of TPG‘s editors and is not influenced by the card issuer.
4 / 5
Go to review

Rewards Rate

10XEarn unlimited 10X miles on hotels and rental cars booked through Capital One Travel
5X5X miles on flights booked through Capital One Travel.
2X2 Miles per dollar on every purchase, every day
  • Intro Offer
    Earn 75,000 bonus miles when you spend $4,000 on purchases in the first 3 months from account opening, equal to $750 in travel

    75,000 bonus miles
  • Annual Fee

    $395
  • Recommended Credit
    Credit ranges are a variation of FICO© Score 8, one of many types of credit scores lenders may use when considering your credit card application.

    740-850
    Excellent

Why We Chose It

The Capital One Venture X card is one of the best all-round travel credit cards ever launched. Not only is it offering a tremendous welcome bonus, but cardholders can earn tons of miles on everyday spending and receive a 10,000-mile anniversary bonus to boot. Its annual fee is $395, but cardholders can count on up to $300 in statement credits toward travel booked through Capital One Travel each year and other valuable benefits like access to Priority Pass lounges and Capital One’s own growing family of airport lounges.

Pros

  • Excellent welcome offer worth 75,000 miles after you spend $4,000 on purchases in the first three months.
  • Up to $300 in annual travel statement credits toward bookings make through Capital One Travel.
  • 10,000 bonus miles (worth $100 toward travel) each account anniversary.

Cons

  • The $395 annual fee might be expensive for some, but this card’s benefits provide much more value than that.
  • If you don’t travel frequently, this might not be the best card for you.
  • Earn 75,000 bonus miles when you spend $4,000 on purchases in the first 3 months from account opening, equal to $750 in travel
  • Receive up to $300 back annually as statement credits for bookings through Capital One Travel, where you'll get Capital One's best prices on thousands of options
  • Get 10,000 bonus miles (equal to $100 towards travel) every year, starting on your first anniversary
  • Earn unlimited 10X miles on hotels and rental cars booked through Capital One Travel and 5X miles on flights booked through Capital One Travel
  • Earn unlimited 2X miles on all other purchases
  • Unlimited complimentary access for you and two guests to 1,400+ lounges, including Capital One Lounges and our Partner Lounge Network
  • Receive up to a $100 credit for Global Entry or TSA PreCheck®
  • Use your Venture X miles to easily cover travel expenses, including flights, hotels, rental cars and more—you can even transfer your miles to your choice of 15+ travel loyalty programs
  • Named editors' choice for "Best New Credit Card of 2021" by The Points Guy
  • Earn 10 miles per dollar when you book on Turo, the world's largest car sharing marketplace, through May 16, 2023