Yes, fog delays and cancels flights regularly

Fog is one of the most common weather reasons for flight delays. It reduces visibility on the runway and in the air, forcing pilots and air traffic control to slow down operations or stop them entirely. When fog is thick enough, planes cannot land or take off safely, even if the engines and systems work perfectly.

The Federal Aviation Administration (FAA) sets minimum visibility standards before flights can operate. These standards vary by runway and airport equipment. If fog drops visibility below those minimums, the airport must reduce the number of planes landing and taking off per hour, or halt operations altogether. A single fog bank can affect hundreds of flights across a region.

Fog delays tend to last longer than other weather delays because fog can persist for hours or even a full day. Unlike thunderstorms that move through quickly, fog often sits in place. This means your flight might be delayed multiple times as conditions fail to improve.

Key Takeaways

  • Fog reduces visibility below the minimums the FAA requires for takeoff and landing, forcing airports to slow or stop operations.
  • Fog delays often last several hours because the weather condition can persist in one location for an extended period.
  • Airports with older equipment have higher visibility minimums and are more vulnerable to fog delays than airports with modern landing systems.
  • If your flight is delayed by fog, you will not receive compensation under U.S. law, because fog is considered an act of nature outside the airline's control.
  • Checking the National Weather Service forecast for your departure and arrival airports before you travel can help you anticipate fog delays.

Why fog affects visibility more than other weather

Fog is a cloud at ground level made of water droplets suspended in air. It reduces visibility to a few hundred feet or less, depending on how dense it is. Pilots cannot see the runway or other aircraft clearly enough to land or take off safely at normal speeds.

The FAA requires different visibility minimums depending on the runway and the airport's equipment. A runway with an Instrument Landing System (ILS) — a precision guidance system — may allow landings in fog as low as 1,200 feet of visibility. A runway without ILS may require 5,000 feet or more. When fog drops below these thresholds, that runway closes to traffic.

Fog is harder to predict than thunderstorms or snow. It can form suddenly in the early morning or late evening, and it can linger unpredictably. This makes it difficult for airlines to know how long a delay will last, so they often hold planes on the ground rather than divert them to another airport.

Which airports are most affected by fog

Coastal airports and airports in valleys are most vulnerable to fog. San Francisco International, Oakland International, and Los Angeles International see frequent fog delays, especially in summer and early fall. Inland airports in mountainous regions like Denver and Salt Lake City also experience fog, though less often.

Older airports with basic runway equipment are hit harder by fog than newer airports with modern landing systems. If an airport has only one runway or runways without ILS, a single fog event can close the entire airport. Larger hubs with multiple runways and advanced equipment can usually keep at least one runway open, even in heavy fog.

The time of year matters too. Fog is most common in early morning hours and during seasons when temperature differences between air and water are greatest — typically spring and fall on the coasts, and early morning year-round in valleys.

How airlines respond when fog delays flights

When fog closes a runway or reduces capacity, the airline's operations center receives updated information from air traffic control about how many planes can land per hour. The airline then decides whether to hold the plane at the gate, delay departure, or divert to another airport.

Most airlines hold planes at the gate during fog delays because diverting to another airport costs fuel, time, and money. If the fog is expected to clear within a few hours, holding is the cheaper choice. If the forecast shows fog lasting all day, the airline may cancel the flight or reroute it through a different airport.

Passengers on delayed flights are usually allowed to deplane and wait in the terminal, though some airlines keep the doors closed if they expect the delay to be short. You will not receive a meal voucher or hotel room for a fog delay, because the airline is not responsible for weather.

Your rights when fog delays your flight

Under U.S. law, you are not may have access to to compensation for a flight delayed or cancelled by fog. The Department of Transportation classifies fog as an act of nature outside the airline's control. The airline has no legal obligation to pay you money, provide a hotel room, or rebook you on another airline.

However, the airline must rebook you on the next available flight to your destination at no extra charge. If the delay is long enough that you need to stay overnight, some airlines offer hotel vouchers as a courtesy, but this is not required by law. Check your airline's policy before you travel.

If you purchased trip insurance or have a credit card with travel protections, those policies may cover losses from fog delays. Read your policy to see what weather events are covered and what documentation you need to file a claim.

How to prepare for fog delays when traveling

Check the National Weather Service forecast for your departure and arrival airports the night before and the morning of your flight. Look for fog advisories or dense fog warnings. If fog is in the forecast, plan to arrive at the airport earlier than usual and expect possible delays.

Book flights on airlines that serve your route with multiple daily flights. If your flight is cancelled or delayed heavily, you have more options to reach your destination the same day. Avoid single-flight-per-day routes during seasons when fog is common in your region.

If you are connecting through a coastal or valley airport known for fog, build extra time into your connection. A two-hour connection that works in clear weather may not be enough if fog delays your first flight. Consider booking a connection of three hours or more during fog season.

read a flight tracking app like FlightAware or your airline's app so you can monitor your flight in real time. These apps show delays as they happen and often display the reason. If fog is causing delays, you will see it reported within minutes of the delay being issued.

The difference between fog delays and other weather delays

Fog delays are usually longer than thunderstorm delays because fog can persist for many hours in one location. A thunderstorm moves through in 30 minutes to two hours, but fog can last from dawn until afternoon or even all day.

Unlike snow or ice, fog does not require runway cleanup or de-icing. The airport does not need to close for maintenance. The only solution is to wait for the fog to lift, which depends entirely on atmospheric conditions the airline cannot control.

Fog is also harder to forecast precisely than other weather. A forecast might say fog is possible, but not predict exactly when it will form, how dense it will be, or how long it will last. This uncertainty makes it difficult for airlines to plan around fog delays.

Frequently Asked Questions

Can planes land in fog with modern technology?

Yes, but only if the airport has an Instrument Landing System and the fog is not too dense. Planes with autoland capability can land in fog as low as 600 feet of visibility at some airports. However, most commercial airports require at least 1,200 feet of visibility, and many require much more. Not all planes have autoland, so even equipped airports may not be able to land all aircraft in heavy fog.

Why don't all airports have equipment to land in fog?

Instrument Landing Systems are expensive to install and maintain, costing millions of dollars per runway. Smaller airports and regional airports cannot justify the cost. Even large airports may have only one or two runways equipped with ILS, so a fog event can still close most of the airport's capacity.

How long do fog delays usually last?

Fog delays typically last two to four hours, but can extend to eight hours or longer if the fog is stubborn. Some fog burns off by mid-morning, while other fog persists all day. The National Weather Service forecast for your airport will give you the best estimate of when fog is expected to clear.

Will my airline refund my ticket if fog cancels my flight?

No, airlines are not required to refund tickets for weather cancellations. They must rebook you on the next available flight at no extra charge, but a refund is not may provide. Check your airline's policy or contact them directly to learn what options you have if your flight is cancelled by fog.

Is fog more common at certain times of year?

Yes. Coastal airports see the most fog in summer and early fall, when warm air moves over cool ocean water. Inland valleys see fog most often in spring and fall. Early morning hours are foggy year-round in many regions. Checking historical weather patterns for your airport can help you avoid fog season when possible.