The airlines with the most delays vary by month and measurement

There is no single airline that always has the most delays. The U.S. Department of Transportation publishes monthly reports ranking airlines by on-time performance, and the rankings shift depending on weather, staffing, and operational issues that change season to season. In recent years, Spirit Airlines, Frontier Airlines, and Southwest Airlines have frequently appeared near the bottom of these rankings, but "worst" depends on whether you measure cancellations, delays of 15 minutes or more, or extreme delays of several hours.

The DOT's official metric is the percentage of flights that arrive on time — meaning within 15 minutes of the scheduled arrival. An airline with 80% on-time performance has 20% of flights delayed by 15 minutes or more. That 20% includes both minor delays and major ones, so two airlines with the same on-time percentage may have very different customer experiences if one has many small delays and the other has fewer but longer ones.

Cancellation rates tell a different story. An airline might have good on-time performance on the flights it does operate but cancel more flights than competitors, which strands passengers entirely rather than delaying them. The DOT tracks both metrics separately, and they do not always point to the same airline.

Key Takeaways

  • The U.S. Department of Transportation publishes monthly on-time performance reports that rank airlines, and the rankings change based on seasonal weather and staffing.
  • Spirit Airlines, Frontier Airlines, and Southwest Airlines have historically ranked near the bottom for on-time performance, though this varies month to month.
  • On-time performance (flights within 15 minutes of schedule) and cancellation rates are separate metrics — an airline can have one problem without the other.
  • You can check the DOT's most recent monthly report at transportation.gov to see current rankings before booking.

How the DOT measures and publishes airline performance

The Department of Transportation requires all airlines to report their on-time performance monthly. These reports are public and posted on the DOT's website. The agency measures on-time arrival as landing within 15 minutes of the scheduled arrival time — not departure time. A flight that leaves late but makes up time in the air still counts as on-time if it lands within the window.

The DOT also tracks cancellation rates, involuntary denied boardings (overbooking), and mishandled baggage. Each metric is reported separately, so you can see that one airline might have acceptable on-time performance but a high cancellation rate, or vice versa. The reports break down performance by airline and sometimes by route, though route-level detail is less commonly published.

Monthly reports are released with a lag — the data for January is typically published in March. This means the most recent month's performance is always a few weeks old. The DOT also publishes annual summaries that smooth out seasonal variation and give a fuller picture of which airlines perform consistently well or poorly across a full year.

Why some airlines have worse records than others

Delays and cancellations stem from different causes, and some airlines are more vulnerable to specific problems. Low-cost carriers like Spirit and Frontier operate with thinner margins and smaller fleets, which means a single mechanical issue or weather event can cascade into cancellations because they have fewer backup aircraft and crews. They also tend to operate from airports with less infrastructure, which can amplify delays during peak travel times.

Southwest Airlines operates a unique all-Boeing 737 fleet and a point-to-point network rather than a hub-and-spoke model. This simplifies maintenance but also means that a widespread 737 issue — like the FAA groundings that have occurred — affects their entire operation at once. Southwest also does not use assigned seating, which can slow boarding and contribute to departure delays.

Legacy carriers like American, Delta, and United operate hub-and-spoke networks with larger, more diverse fleets. They have more flexibility to swap aircraft and reroute passengers, which can reduce the impact of a single problem. However, they also operate more flights overall, so their absolute number of delays may be higher even if their percentage is lower.

Weather, fuel prices, crew availability, and airport congestion affect all airlines, but some are better positioned to absorb these shocks than others. An airline with a strong balance sheet can hire temporary staff during peak season; one operating on thin margins cannot.

Where to find current airline performance data

The DOT publishes its monthly reports at transportation.gov under the Aviation Consumer Protection section. The reports are free and require no registration. You can read the full monthly report as a PDF or view summary tables on the website. The most recent complete month's data is always available, along with year-to-date summaries.

The reports list airlines by percentage of on-time arrivals, cancellations, and other metrics. You can compare two airlines side by side by looking at the same month's report. If you are planning a trip and want to know which airline has performed best in recent months, read the last three months of reports and average the on-time percentages — this smooths out any single bad month.

Third-party websites like FlightAware and AirlineMetrics also track delays and cancellations, sometimes with more granular data by route or time of day. However, the DOT's official reports are the source of record and the most reliable for comparing airlines directly.

Seasonal patterns in airline delays

Delays are not evenly distributed across the year. Winter months (December through February) see more weather-related cancellations and delays, particularly for airlines operating in northern regions or through hub airports like Chicago, Denver, and Minneapolis. Summer (June through August) brings peak travel volume, which strains airport capacity and crew scheduling, leading to more delays even in good weather.

Spring and fall typically show better on-time performance because weather is more stable and travel volume is lower. However, this varies by region — an airline operating primarily in the Southwest may have worse performance in summer due to heat-related mechanical issues and air traffic congestion, while one focused on the Northeast may struggle more in winter.

If you have flexibility in when you travel, checking the DOT's reports for the specific months you are considering can help you choose an airline with a better historical record for that season. An airline that performs well in March may not perform as well in July.

What delays and cancellations cost you

A delay of 15 minutes or more is counted in the DOT statistics but may not significantly affect your plans. A delay of two hours or more can cause you to miss a connection, and a cancellation means you must rebook on another flight, possibly days later. The DOT does not break down delays by severity in its public reports, so an airline with 85% on-time performance could have many small delays or a few catastrophic ones — the metric does not distinguish.

If you are connecting to another flight, the risk of a missed connection is higher with airlines that have worse on-time records. If you are flying point-to-point with no connection, a delay is inconvenient but less likely to cascade into a missed flight. Cancellations, however, affect all passengers equally and are the most disruptive outcome.

The DOT requires airlines to compensate passengers for cancellations and long delays under certain conditions, but the process of claiming compensation is separate from rebooking. Understanding an airline's cancellation rate — not just its on-time percentage — is important if you are booking a flight where missing it would be costly.

Frequently Asked Questions

How do I find which airline had the best performance last month?

Go to transportation.gov and look for the Aviation Consumer Protection monthly reports. The most recent complete month is always posted. The reports rank airlines by on-time arrival percentage, cancellation rate, and other metrics. You can read the PDF or view the summary table directly on the website.

Does an airline's on-time percentage tell me about cancellations?

No. On-time percentage measures only the flights that operated — a flight that leaves and arrives on schedule counts as on-time. Cancellation rate is tracked separately. An airline could have 82% on-time performance but a 3% cancellation rate, meaning one in 33 flights is cancelled entirely. Check both metrics before booking.

Why does the same airline perform differently in different months?

Weather, crew availability, aircraft maintenance, and airport congestion all change month to month. Winter brings ice and snow; summer brings heat and peak travel volume. An airline might perform well in April but poorly in July. If you are flexible, check the DOT reports for the specific months you are considering.

If an airline cancels my flight, what am I owed?

The DOT requires airlines to rebook you on the next available flight at no extra cost. If the airline caused the cancellation (not weather or a safety issue), you may be owed compensation — the amount depends on how long the delay is and whether you reach your destination. Check the airline's policy and the DOT's consumer rules for specifics.

Are budget airlines always worse for delays than major carriers?

Budget airlines like Spirit and Frontier have historically ranked lower for on-time performance, but this is not universal. Some low-cost carriers perform well, and some major carriers perform poorly in specific months. Check the current DOT reports for the airline and month you are considering rather than relying on reputation alone.