Most flights arrive on time, but delays happen on roughly one in four days

About 75 to 80 percent of flights in the United States arrive within 15 minutes of their scheduled time. That means on any given day, roughly one in five flights experiences a delay of 15 minutes or more. The exact rate shifts by season, airport, and airline — winter months see more delays than summer, and major hubs like Atlanta and Chicago have higher delay counts straightforward because they handle more flights.

The U.S. Department of Transportation tracks on-time performance for all airlines and publishes the data monthly. A delay is officially counted when a flight arrives 15 minutes or later than scheduled. Delays of less than 15 minutes do not appear in the statistics, even though passengers experience them.

Key Takeaways

  • About one in five flights experiences a delay of 15 minutes or more, though this varies by season and airport.
  • Winter weather, especially snow and ice, causes the highest delay rates; summer typically has the fewest delays.
  • Weather accounts for roughly 70 percent of all delays, while mechanical issues, crew problems, and air traffic control account for the rest.
  • Major hub airports like Atlanta, Dallas, and Chicago have more total delays because they handle far more flights than smaller airports.
  • The time of day matters: afternoon and evening flights delay more often than morning flights.

Why winter has more delays than other seasons

Winter months — December through February — see delay rates climb to 20 to 25 percent or higher in regions that experience snow and ice. Snow on runways, icing on aircraft, and reduced visibility all force airlines to slow operations. De-icing procedures add 15 to 30 minutes to turnaround times, and when multiple flights need de-icing, the backlog spreads across the day.

Spring and fall sit in the middle, with delay rates around 15 to 18 percent. Summer, particularly June through August, typically has the lowest delay rates — often 12 to 15 percent — because clear skies and dry runways allow faster operations. However, summer also brings thunderstorms in the afternoon and evening, which can spike delays at specific airports for a few hours at a time.

Weather causes roughly 70 percent of all delays

Thunderstorms, snow, fog, and high winds are the leading reasons planes do not depart or arrive on time. A single thunderstorm over a major airport can delay dozens of flights because pilots cannot take off or land safely in severe weather. The delay ripples forward: a plane stuck on the ground in Chicago cannot reach its next destination on time, which delays passengers waiting for that plane in Denver.

The remaining 30 percent of delays split among mechanical issues (engine problems, hydraulic leaks, avionics failures), crew scheduling problems (a crew member running late or exceeding work-hour limits), air traffic control delays, and airline operations (overbooking, late passenger boarding, or ground crew shortages). Mechanical delays tend to be longer — often 30 minutes to several hours — because the problem must be diagnosed and fixed before the plane can fly.

Afternoon and evening flights delay more than morning flights

Early morning flights — those departing before 9 a.m. — have the best on-time record, with delay rates around 10 to 12 percent. Afternoon flights (noon to 6 p.m.) see rates climb to 18 to 22 percent. Evening flights (after 6 p.m.) often hit 20 to 25 percent because delays from earlier in the day have accumulated.

A plane that departs late from its first flight of the day carries that delay into its second flight, then its third. By evening, a single morning delay has cascaded through multiple flights. Airlines also schedule more flights in the afternoon and evening, which means more planes competing for limited runway time during peak hours.

Major airports have higher delay counts but not always higher rates

Atlanta Hartsfield-Jackson, Dallas-Fort Worth, and Chicago O'Hare handle the most flights in the country, so they also report the most total delays. However, their delay rates — the percentage of flights delayed — are often close to the national average. A smaller airport like Bozeman or Rapid City may have a higher percentage of delays on any given day, but fewer total flights means fewer people experience those delays.

Airports in regions with frequent weather problems — Denver (afternoon thunderstorms), San Francisco (fog), and Minneapolis (winter snow) — tend to have higher delay rates year-round. Conversely, airports in dry, mild climates like Phoenix and Las Vegas have some of the lowest delay rates in the country.

Delays have stayed roughly the same for the past decade

The on-time performance of U.S. airlines has remained relatively stable since 2010, hovering between 75 and 82 percent. There was a slight improvement around 2017 to 2019, but the rate has not dramatically improved or worsened over the long term. The number of flights has grown, so more people experience delays in absolute terms, but the percentage of delayed flights has not changed much.

Airlines have invested in faster turnarounds, better scheduling software, and improved maintenance procedures, but these gains are offset by increased air traffic and congestion at major hubs. Weather remains the dominant factor, and no technology has yet reduced its impact on flight schedules.

How to find delay information for a specific flight or airline

The Department of Transportation publishes monthly on-time performance reports for every airline. You can search by airline name to see their delay rate for the past month. FlightAware and other flight-tracking websites show real-time delays for specific flights and airports, updated minute by minute.

If you are checking a flight before you book, look at the scheduled departure time and the airport's typical delay rate for that time of day and season. A 2 p.m. flight in February from Denver is statistically more likely to delay than a 7 a.m. flight in June from Phoenix. This does not mean the flight will delay, only that the odds are higher.

Frequently Asked Questions

What counts as a delay?

The Department of Transportation counts any flight that arrives 15 minutes or later than scheduled as delayed. Delays of 14 minutes or less do not appear in official statistics. Airlines may also track on-time performance using different definitions for internal purposes.

Do airlines report delays differently than the government does?

Airlines report their own on-time performance to the Department of Transportation, which publishes the data. Airlines cannot hide delays — the government tracks every commercial flight. However, some airlines may define "on-time" slightly differently in their own marketing materials, so always check the government data for the most consistent comparison.

Is one airline more reliable than another?

Yes. Some airlines consistently rank in the top tier for on-time performance, while others rank lower. The Department of Transportation publishes monthly rankings by airline. However, the airline you fly matters less than the airport, time of day, and season — a flight on a reliable airline departing at 5 p.m. in February from a snowy city is still more likely to delay than a flight on a less reliable airline departing at 7 a.m. in June from a dry city.

Are delays getting worse?

No. The percentage of delayed flights has remained stable for over a decade, around 20 to 25 percent. More people fly now than in the past, so more people experience delays in total numbers, but the rate has not worsened significantly.

Can I predict whether my flight will delay?

You can estimate the odds based on the airport, time of day, season, and current weather, but you cannot predict with certainty. Check the weather forecast for your departure and arrival cities, look at real-time delays on FlightAware, and arrive early. If severe weather is forecast, expect a higher chance of delay.