How Weather Impacts Major Airports in the United States

Weather impacts airplane flights and airport operations in a variety of ways and is a major concern for the aviation community (Kulesa 2003).

Pilots need to avoid weather that will endanger a flight, and also need to understand how weather will impact the performance of the aircraft. Air traffic controllers need to understand where hazardous weather is located so that they can direct aircraft to safety or hold aircraft on the ground (Andrews 1993). Dispatchers need to understand how the environmental temperatures will affect the takeoff and landing distances (Subbotin and Gardner 2013). Passengers need to know whether or not an upcoming weather event will cancel future flights. Airlines want to reduce the number of delayed and cancelled flights and need to take into consideration weather specific to each airport and region (Hansen and Bolic 2001). From this small number of examples one can understand the significant impacts of weather phenomena on the aviation community.

Besides impacts to the operations of airlines and other aviation community members, weather impacts the economic performance of the aviation community by creating delays and cancellations. The economic costs of air traffic delays to the U.S. economy are vast and far-reaching; in 2007, the total cost of airline delays was $41 billion dollars (Joint Economic Committee 2008). Weather plays a significant role in creating delays and cancellations and may cause up to 70% of the delays in the National Airspace System (NAS) (Kulesa 2003). While forecasts have allowed aviation operators to make some adjustments to operations, weather continues to impact airlines since schedules are created and finalized weeks in advance. 

By better understanding the expected weather of an airport and how each specific weather type impacts each individual airport, planners and schedulers can create schedules that work to eliminate the impacts of expected weather predictions. For example, if an airport is prone to early morning fog or icing conditions in winter (e.g., December and January), an airline scheduler can adjust the schedule to take into account low visibility airport or aircraft deicing operations. Identifying weather types and severity most related to flight cancellations and delays means better success in adjusting schedules 

Here, we use historical hourly weather records and Federal Aviation Administration (FAA) performance datasets, including the Aviation System Performance Metrics (ASPM) to determine the relationship between flight cancellations and delays due to weather type (drizzle, rain, snow, fog, mist, and haze), descriptors (freezing and thunderstorms), and weather severity (none, mild, moderate, and severe). The analysis is completed on the 77 airports reporting data to the FAA, with a focus on 10 major U.S. airports with long weather records and high density flight traffic. 

The 77 ASPM airports are shown below, with those highlighted for detailed analysis in red. 

Locations of the 77 ASPM airports. Airports in red are highlighted in this work for considering regional impacts of specific weather types and events.

It is important to look at airports individually when determining the impact of weather on operations. First, climates vary across the United States, causing differences in weather delays and cancellations from one airport to another. For example, airports in the Gulf Coast portion of the United States may be more concerned about thunderstorms or rain instead of snow due to their southerly location. Another reason to look at airports individually is that airports have different layouts, terrain features, proportions of carriers, and airline schedules that cause varying responses to specific weather types. For example, some airports may better handle fog or low visibility operations due to the layout of runways.

Notably, for all 10 airports that were analyzed individually, the largest arrival and departure delays are due to severe weather. Departures are delayed, on average, by 65.8 min and arrivals are delayed by 62.9 min. JFK in New York experiences the longest departure delays (80 min) whereas Salt Lake City in Utah experiences the shortest departure delays (50 min). O’Hare International Airport in Chicago experiences the longest arrival delays (79 min) whereas Salt Lake City also experiences the shortest arrival delays (49 min). Airport efficiency is most impacted by severe weather. On average the 10 airports showed an 18% reduction in airport efficiency. The airport that is most impacted by severe weather was Dallas Love Field Airport. The airport least affected by severe weather is San Francisco International. In summary, the table below clearly shows that for all airports, as the severity of the weather increases so does the overall impact on airport delays (arrivals and departures) and airport efficiencies.

Airport Scores

Statistics for weather severity categories (%) with most common severity in bold, average airport departure delays (minutes) with the longest delay in bold, average airport arrival delays (minutes) with the longest delay in bold, and airport efficiency scores (%) for weather impacts with the lowest airport score in bold. The mean across all airports is included as well.

Average airport departure delays are most impacted by freezing with an average of 83 min across all airports, thunderstorms with an average delay of 74 min across all airports, and fog with an average of 72 min across all airports. The airports most impacted by freezing include JFK,  Atlanta International, Minneapolis−Saint Paul International, Salt Lake City, and Seattle-Tacoma International with an average departure delay of 96.4 min. The airports most impacted by thunderstorms include JFK, O’Hare International, Dallas Love Field Airport, and San Francisco International with an average departure delay of 90.6 min. The airports most impacted by fog include Miami International and Phoenix Sky Harbor International with an average departure delay of 98 min.

Similar to departures, across all airports the average airport arrival delays are most impacted by freezing with an average of 67 min, thunderstorms with an average of 68 min, and fog with an average of 74 min. The airports most impacted by freezing include JFK, Atlanta International, Minneapolis−Saint Paul International, Salt Lake City, and Seattle-Tacoma International with an average arrival delay of 74 min. The airports most impacted by thunderstorms include JFK, O’Hare International, Dallas Love Field Airport, and San Francisco International with an average arrival delay of 84 min. The airports most impacted by fog include Miami International, Salt Lake City, and Phoenix Sky Harbor International with an average arrival delay of 90 min.

The combination of weather events in each city results in decreases in airport efficiencies. For JFK, freezing precipitation and thunderstorms have the highest overall impact. For Atlanta International, freezing precipitation, snow, and thunderstorms have the overall greatest impacts to efficiency. The largest reduction in efficiency for both Miami International and Phoenix Sky Harbor International is due to fog. Like JFK and Atlanta International, Minneapolis−Saint Paul International and Salt Lake City are most impacted by freezing events. Thunderstorms impact O’Hare International, Dallas Love Field Airport, and San Francisco International the most.

Departure and Arrival Cancellations

The most common cause for departure and arrival cancellations was freezing precipitation during the winter months December–February (JFL, Atlanta International, Minneapolis−Saint Paul International, O’Hare International, Salt Lake City, and Seattle-Tacoma International). For departures, fog was an important cause for cancellations in Miami International, Phoenix Sky Harbor International, and San Francisco International. O’Hare International and Dallas Love Field Airport also experience a high occurrence of cancellations due to fog and thunderstorms. Behind winter weather, fog is the most common reason for cancellations at Minneapolis−Saint Paul International and Salt Lake City. For Miami International, the most cancellations occur in August–October and are likely associated with high numbers of cancellations per hour due to rain, thunderstorms, mist, and moderate and severe wind speeds. Airports that do not typically experience winter weather (San Francisco International, Phoenix Sky Harbor International, Miami International) have cancellations dominated by obscuring phenomena such as fog and haze or those related to precipitation such as drizzle, rain, or mist. Arrival and departure cancellations occur at similar frequencies for the same weather type. In summary, regional and seasonal weather patterns (e.g., freezing precipitation or thunderstorms) determine the overall impact on airport departure and arrival cancellations as well as airport efficiencies.

For all airports, delays and decreases in efficiency (lower airport scores) increase as the severity increases from “none” to “severe”. The variability for delays between airports is a result of the frequency of occurrence of the weather types/descriptors. For example, impacts to Atlanta International increase with freezing precipitation, snow, and thunderstorms and result in the greatest reduction in efficiency of airport operations. The infrequent occurrences of snow and freezing precipitation mean that other weather phenomena, such as fog or thunderstorms, are likely to have higher annual impacts on the operating efficiency of Atlanta International. Unlike Atlanta International, O’Hare International experiences greater delay impacts from thunderstorms. 

Chicago O'Hare International Airport. Photo by Evan R.

For Dallas Love Field Airport thunderstorms and fog cause the greatest reduction in efficiency and result in more delays, unlike snow or freezing precipitation. Dallas Love Field Airport’s airport configuration or the smaller number of flights compared to Atlanta International or O’Hare International may mean that Dallas Love Field Airport is able to better handle snow and ice events. For Minneapolis−Saint Paul International, the largest reductions in efficiency come from freezing precipitation, thunderstorms, and fog. However, these are less common than other phenomena, meaning that snow or rain observations have a greater overall impact. This also suggests that Minneapolis−Saint Paul International is equipped to handle snow better than other airports, such as Atlanta International, where snow is less common. 

Each airport has its own unique annual cancellation cycle for departures and arrivals. Atlanta International has a majority of arrival and departure average weather cancellations in January, February, and December. For Atlanta International both freezing precipitation and snow vastly outnumber all other weather types in number of cancellations. This indicates that the vast majority of winter weather cancellations are caused by snow and freezing precipitation. O’Hare International’s weather cancellations occur in winter as a result of overall poor weather conditions and higher occurrences of frozen precipitation and fog. Freezing precipitation, followed by fog, is responsible for the highest number of cancellations. Snow, thunderstorms, severe visibility, and severe wind are also responsible for a relatively high number of cancellations per hour. For Dallas Love Field Airport, weather cancellations peak in December, January, and February (with February showing the highest peak) and in September. It is difficult to pinpoint the cause of weather cancellations for Dallas Love Field Airport in September due to the relatively fair weather during that time period. There is a small peak in weather cancellations in May that coincides with the peak in thunderstorms. 

For Minneapolis−Saint Paul International December, January, February, and March have the highest monthly weather cancellations. This is due to poorer weather conditions as a result of frozen precipitation, fog, and reduced visibility. Freezing precipitation, fog, and severe visibility all have the highest cancellation rates. Most weather cancellations in JFK occur in December, January, and February and are most likely a result of winter storms. Freezing precipitation and severe wind speed, in that order, have the two highest cancellation rates; however, both events are relatively rare in the year. Snow has the third highest cancellation rate and is relatively common in the winter months, suggesting that it is responsible for a large share of the weather cancellations. December and January have the highest number of weather cancellations for Salt Lake City and are most likely the result of poor visibility, low ceilings, frozen precipitation, and obscuring phenomena. Fog and freezing precipitation have the highest cancellation rate along with the more severe weather conditions. Conditions with reduced visibility are especially hazardous in mountainous areas like in Salt Lake City due to the losses of visual situational awareness in relation to terrain. This may be the reason for the high number of cancellations during periods of fog, severe ceiling heights, and severe visibility.

Weather-induced cancellations in Seattle-Tacoma International are most often in December and January as a result of winter weather. Overall, freezing precipitation and snow are responsible for the highest number of hourly cancellations.

At San Francisco International, most weather cancellations occur during December, January, and February and are related to low visibility and low ceiling heights due to events like drizzle, rain, fog, and mist. Phoenix Sky Harbor International’s general weather patterns favor few monthly cancellations, although cancellations do peak in winter as with other airports. The low numbers also suggest that weather cancellations at Phoenix Sky Harbor International are likely a result of weather en route or at other airports. For Miami International, the peak in wintertime weather cancellations is likely associated with weather at other airports rather than at Miami International itself. However, the August to October weather cancellation peak is most likely associated with hurricanes and tropical storms.

Phoenix Sky Harbor International Airport. Photo by Colin Lloyd.

The results presented in this work clearly identify a strong link between a reduction in airport efficiency and weather. The impacts on airport operations are varied and complex ranging from weather (the focus of this work) to issues with security, which are not accounted for in this analysis. For example, in the instance of precipitation, slippery runway and taxiway conditions may require slower taxiing speeds and greater distance between aircraft on the ground; this may reduce the overall efficiency of the airport since fewer aircraft may be allowed on the movement areas and those aircraft may be taxiing at slower speeds (Oda et al. 2010). Slippery ramp areas may also increase the difficulty of other ground operations, such as pushing back an aircraft or loading cargo, and may result in gate delays or other performance decreases. The negative impacts caused by frozen or freezing precipitation require the implementation of various snow and ice removal techniques. Many of these techniques, such as applications of chemicals, can close runways or taxiways and impede airport operations. Many aircraft have equipment to remove or prevent the buildup of ice on certain areas but these systems may not be effective on the ground. To ensure that necessary aircraft surfaces are not contaminated with ice, ground deicing must occur before takeoff. This increases the cost and complexity of operations resulting in decreased economic and operational performance. When visibility is impacted, airports may not be able to operate in the optimal condition, thereby reducing the number of aircraft an airport can handle. For example, San Francisco International Airport cannot use parallel approaches during low visibility conditions, reducing capacity by 50% (San Francisco International Airport 2010).

The most important finding is that every airport delay and cancellation analysis is different and it is important to look at each airport individually. Airports all have their own unique climates, layouts, and operation procedures, meaning that all airports will be affected differently by weather. Some airports handle certain weather phenomena better or worse, such as freezing precipitation or low visibility, and weather phenomena may not be as frequent at one airport as it is at another airport. For example, a snowstorm in Atlanta has a larger impact (e.g., delays or cancellations) than at O’Hare International, which is routinely impacted by snow and prepared for severe winter weather. Finally, airports all have different layouts and surrounding terrain that may make operations in certain weather types more challenging than what would be at another airport. In all, generalizing weather impacts for all airports may prove an ineffective way to understand how weather impacts commercial operations. Also, while overall delay and cancellation statistics at a specific airport can be impacted by weather events at another airport, there is no current way to truly remove this type of impact. Delays and cancellations overall are not solely caused by one factor but rather by multiple factors that impact each other.

This article has been excerpted and edited specifically for the AMS Weather Band from a longer article "Meteorological Impacts on Commercial Aviation Delays and Cancellations in the Continental United States" by Christopher J. Goodman and Jennifer D. Small Griswold, which was published in the Journal of Applied Meteorology and Climatology. Any errors and omissions can be attributed to AMS Staff.