How do pilots manage to take off during a snowstorm?

It's that season again: Deep winter in the Northern Hemisphere brings significant disruptions to major airports due to snow, sleet, and severe weather. If you traveled through New York's John F. Kennedy International Airport (JFK) in 2018, you might still remember the bomb cyclone that paralyzed this key entry point to the U.S.

If you frequently pass through Chicago's O'Hare International Airport (ORD), you're likely familiar with the frustrations of delays caused by winter weather. London's Heathrow Airport (LHR) isn't spared either. You've probably experienced the discomfort of sitting on a taxiway as snow swirls outside, or had your flight canceled due to fog.

Another storm is brewing just ahead of the hectic Christmas travel season, threatening to bring adverse weather to hubs across the Great Plains, Midwest, and East Coast.

While travelers deal with chaos at the airport or on their phones trying to rebook, what challenges do pilots face?

What do these weather phenomena look like from the cockpit? How do airline pilots handle challenging winter conditions, from snowstorms to high winds? Are there specific weather scenarios that pilots dread more than others? For insights, we consulted an expert: a pilot who operates Boeing 787s for a leading international airline and has experienced various weather conditions globally.

In an email, he shared his experiences flying in harsh winter weather. To ensure his candidness, we've kept his name anonymous and made light edits for brevity and clarity. Here's his account.

Snow is the biggest challenge.

Different weather conditions present unique difficulties. Strong winds can result in turbulent takeoffs and landings. When the wind crosses the runway, we must approach "crabbed" to maintain a straight path. The true test of our skills occurs just feet above the runway, where we must align the aircraft’s nose using a few approved techniques while keeping it on the centerline. Ask any pilot about their most rewarding moment at work, and many will recount a successful crosswind landing.

Fog also demands our attention. When you're racing down the runway at 195 miles per hour with only 250 feet of visibility, you need to be on top of your game. Strictly rehearsed procedures for such scenarios ensure the safety of everyone on board.

Nonetheless, it’s likely that snow and ice conditions pose the greatest challenge to our professional skills.

While you're in a taxi en route to the airport, your pilots are also making their way, contemplating the hurdles that lie ahead. Days of bad weather demand heightened focus and careful consideration.

In the early stages of a pilot's training, a significant emphasis is placed on understanding weather and its impact on flights. We are taught from the beginning to respect weather conditions and never to underestimate their power. Mother Nature is a formidable force.

How intense is the snowfall? What’s the current temperature? What type of snow are we dealing with? How is the wind behaving? All these considerations flood our minds before we even reach the airport.

The primary danger to flight safety in snowy conditions is the contamination of the aircraft's surfaces. The wings are designed so intricately that any accumulation of snow or ice can significantly compromise the aircraft's performance.

For an aircraft to generate lift and ascend from the runway, it needs airflow over the wings. This airflow is what enables flight—the engines are responsible only for producing forward motion. Before every takeoff, pilots calculate the necessary speed for a safe lift-off, taking into account the aircraft's weight, weather conditions, and runway status at departure. Once we reach this critical speed, referred to as "Vr," we gently pull back on the controls, and the aircraft rises into the sky.

However, this speed relies on a clean wing, free from any snow or ice buildup. Contaminants on the flight surfaces can disrupt airflow and reduce lift, resulting in a Vr speed that is too low—leading to potentially catastrophic outcomes.

Prior to each flight, one of the pilots conducts a thorough walk-around inspection of the aircraft to assess its condition. In snowy conditions, a significant focus is on identifying any contamination. The engines, wings, and external sensors are meticulously examined. Often, the only way to inspect the upper wing surface is by looking out of a cabin window, so don’t be surprised if you see a pilot doing this—it’s a reassuring sign!

Based on these inspections, we determine the appropriate de-icing procedure necessary to ensure the aircraft is ready for takeoff. If there’s any uncertainty about the extent of the contamination, we always err on the side of caution. More de-icing is preferable to insufficient amounts.

De-icing on the cake

We share your desire to be with our families and friends. While we are always conscious of timeliness, we recognize that safety is often at odds with punctuality. It’s our responsibility to find that delicate balance.

As we sit at the gate, waiting for de-icing, we understand you have connections to catch, meetings to attend, and a longing to return home. Yet, aviation history is filled with examples of pilots who took shortcuts to save a few minutes, only to deeply regret those decisions later.

But why does de-icing take so long?

Aircraft can be de-iced in two ways: either with the engines turned off at the gate or with the engines running in a designated de-icing area. This choice depends on the airport and the facilities available. Airports that frequently encounter snow and ice, like Montreal-Trudeau International Airport (YUL), typically have remote de-icing facilities. In contrast, airports that face these conditions only occasionally, such as Newark Liberty International Airport (EWR), usually have de-icing trucks that operate at the gate.

I can already hear you wondering why large airports like Newark don’t simply invest in better facilities. The answer lies in space and cost considerations. Remote de-icing pads are significantly more expensive and occupy a lot of room. Would you invest in an expensive electric snow-clearing machine for your home when a simple shovel suffices for the few days it snows?

The de-icing procedure can take anywhere from a few minutes to half an hour, depending on the amount of snow and ice present on the aircraft. With a limited number of de-icing trucks available, it's easy to see how delays can quickly accumulate.

Throughout this time, we remain calm in the flight deck. There's no need to rush. It's best to let trained professionals handle the process, and once de-icing is complete, it’s complete.

After de-icing is finished, the countdown begins. If snow is still falling, it won't be long before it starts to accumulate on the wings again. This duration is known as holdover time; we calculate how long we have before we must take off or get de-iced again. This timing varies based on the de-icing fluid used, the air temperature, and the type of precipitation occurring.

While it may feel like a race against the clock to get airborne, our primary responsibility is safety. If the taxi to the runway takes too long and our holdover time expires, we must return for another round of de-icing. This may lead to further delays and frustration for you, but rest assured, we are committed to keeping you safe.

Yes, taking off from a snow-covered runway is possible,*

As we approach the runway, our focus sharpens significantly. We're intently listening to air traffic control. When visibility is compromised due to snow, we must create a mental map of the positions of other aircraft around us.

This is why ATC communicates exclusively in English, the universal language of aviation. By paying attention to the instructions given to other planes, we can determine if one is preparing to land or another is taking off further down the runway.

ATC will also provide us with details about the runway conditions, which brings me back to my earlier point. You can take off from a snow-covered runway... but it all depends on the level of slipperiness and the amount of accumulated snow.

Snow comes in various forms, from wet to very dry, largely influenced by air temperature. In regions like northern Canada and Scandinavia, where snow is typically dry, there are occasions when takeoff is feasible even with visible snow on the runway, depending on its slipperiness.

Most airports utilize specialized vehicles equipped with rollers to assess the runway's slipperiness. This data is relayed to pilots, helping them determine their aircraft's performance for takeoff and landing, as previously discussed.

Conversely, wetter snow increases runway slipperiness, commonly seen during snowstorms along the Eastern Seaboard of the U.S. when temperatures are milder. In such cases, the runway must be cleared and treated with anti-ice materials.

This process can understandably take time, during which we can do little more than wait. Once again, it’s all for your safety.

As we approach the runway for takeoff, we continually monitor the weather to verify that our previously calculated performance metrics are still accurate. If conditions have shifted, we must recalculate, which can take additional time.

We will only notify air traffic control of our readiness for departure once we are confident that the aircraft is completely clear of snow and ice, and our performance calculations remain valid.

In summary

When we position ourselves on that runway with over 200 lives aboard, our priority is to ensure a safe takeoff. By rigorously adhering to all procedures, we guarantee your safe arrival at your destination, even if it takes a little longer than expected.