The 5 Most Common Reasons For Flight Delays In The U.S.

by SharonKurheg

Everyone has stories about flight delays. Joe and I just had 2 flights delayed on our way to and from NYC.

Of course, you have to be careful because some flights can become “un-delayed.” And there are things you can do to prepare for a weather-related delay and a few things you can do if it looks like you may miss your connecting flight because of the delay of your first flight. But more often than not, a delayed flight is just delayed…or becomes MORE delayed ;-).

So what causes all these delays? People love to say “weather.” Or “staffing.” But how often do each of those, and other things, actually contribute to a flight delay?

Fortunately, the U.S. Bureau of Transportation Statistics (BTS) keeps track of all that.

How often are airplanes on time?

To understand how often planes are delayed and why, it helps to know how often they’re on time. And that all depends on the year, really. Here’s what they were for the past few years:

  • 2018: 79.38% of all flights were on time
  • 2019: 79.21% of all flights
  • 2020: 84.63%
  • 2021: 81.19%

So, except for 2020, they tend to hover at around roughly 80% of the time.

2020 was, of course, an outlier. Virtually all airlines were “on pause” for a while, and even when they started flying again, there were significantly fewer planes in the sky than in pre-pandemic times. Some planes also flew at a higher altitude during the earlier days of COVID (because they could!), which could have potentially helped them fly faster without using as much fuel and therefore get to their destination faster.

But anyway, here are the 5 most common reasons for flight delays in the U.S. in 2021 (the most recent statistics available for a full year):

1. Air Carrier Delay (6.57%)

This category includes all delays that came, as per BTS, “due to circumstances within the airline’s control.”

So that could include maintenance issues, or if a crew is waiting for flight attendants or pilots to show up. It would also go under “Air Carrier Delay” if there’s a slow down in cleaning the aircraft, loading baggage, or fueling.

For 2021, Air Carrier Delays affected 6.57% of all flights within the U.S. That’s a percentage higher than any other reason, as well as almost double the rate of Air Carrier Delay issues in 2020 (3.35%) and over a point higher than the rate for 2019 (5.23%).

2. Aircraft Arriving Late (5.34%)

Due to the logistics of planes (where they’re going and where they need to go afterward), just one event that’s making delays can make for a snowball effect of flight delays and cancellations at a U.S. airport – sometimes for the rest of the day or even into the next day. A good example would be when Dallas has such horrible winds in October, 2021 that it eventually wound up causing American Airlines to cancel over 2,300 flights.

The BTS calls this, “a previous flight with the same aircraft arrived late, causing the present flight to depart late.”

So in 2021, weather issues, or other delays that caused aircraft to arrive late were the reason for 5.34% of all total flights being delayed. Just for the record, in 2020, only 2.34% of all flights arrived late. But again…COVID.

3. National Aviation System Delay (4.12%)

This is sort of the “it doesn’t fit anywhere else, so let’s put it HERE” category. According to the BTS, this includes delays and cancellations that can be blamed on the national aviation system. Examples would be, “non-extreme weather conditions, airport operations, heavy traffic volume, and air traffic control.”

In 2021, most of this category of delay was due to non-extreme weather (46.76%), volume (39.44%), closed runway (8.82%), and “other” (4.79%).

4. Canceled (1.72%)

Believe it or not, flights being canceled are pretty rare, according to the data tracked by BTS.

In 2018, 1.62% of all flights were canceled. In 2019, it was 1.82%. 2020 saw 5.99% of flights canceled but, as always, #thankscovid.

It will be interesting to see what 2022’s numbers look like, with all the meltdowns airlines have had in the first 4 months of the year.

5. “Extreme” Weather (.74%)

Although “weather” is claimed to be the reason for a lot of flight delays, “extreme” weather was responsible for less than 1% of all flight delays in the U.S. in 2021. That being said, that could just be how BTS categorizes “extreme weather.”

According to the bureau, when combined with the other weather categorization in the National Aviation System Delay category, and how weather impacts aircraft arriving late, weather can be responsible for upwards of 34% of all flight delays. It all depends on what month you’re talking about.

Case in point, for 2021, 33.85% of all flights in February were delayed by weather. But in November of the same year, weather delays had dropped to 11.05%. And let’s not even talk about the daily afternoon deluges in Florida!

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