More Than You Ever Wanted to Know About Flight Delays

How do some people always stay at luxury hotels without paying full price? How does that one friend of yours always seem to find parking? How does your coworker have so many points to travel free? How do travel nerds know about flight delays before they happen?

The answers to questions like these belong in a category of knowledge that is invisible to most of us: useful tricks that might make your life a little bit better, but that you’ll never hear about. You could try learning this knowledge by spending days reading Reddit threads and posts on forums from the early 2000s, but even then, there’s no guarantee you’ll find the secret wisdom you are looking for.

The best and easiest way to learn about this invisible knowledge is to have a nerdy friend who just knows stuff, and who can talk about that stuff in a clear and useful way. Like having a mechanic friend when your car breaks down. It’s a great feeling to learn this type of knowledge.

Today, we’re that nerdy friend. And the topic is predicting if your flight is going to be delayed.

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To be clear, flying is great. It’s crazy you can fly around the world for so cheap. The process of flying, though, is kind of terrible. And flight delays might be the worst offender.

It’s not just that delays happen. It’s that, when they happen, you often don’t hear about them until the last minute. You might assume this is because the airline doesn’t know about the delays until the last minute either. That’s not true.

Your airline often knows that your flight might be delayed—or will be delayed—far before they let you know about it. That’s because it’s not really in their best interest to be transparent with you. They don’t want you and all the other passengers to freak out, to make itinerary changes, or to bother their already-busy (and often nonexistent) airport staff. They’d rather have you quiet and at the gate until the last possible moment. Most airlines will never warn you about a potential delay, and they will rarely tell you about a confirmed delay the moment they learn that it’s going to happen. TL;DR: airlines gatekeep delay intel.

(Some airline apps and notification systems are also just built on archaic tech and don’t work properly.)

Good news for you is that it’s surprisingly easy to predict flight delays, sometimes even weeks before you fly. And you can do it with information your airline doesn’t provide you. Here is our simple guide.

Note: If you’re wondering, “Who are these guys to speak so authoritatively?” The real answer is that it doesn’t matter, because these are facts, and

we don’t need credentialsto tell you about them. The nicer answer is that we have spent a lot of time traveling. One of us even occasionally works for what is probably the best flight tracking app,

Flighty. So we have the credentials too, if you wanted those.

Before your book your flight

Flights have performance records, just like athletes or accountants. Some are much better than others. The concept may sound weird because airlines have never told you about it, but just think: would it boost conversions to show customers a “This flight is late 87% of the time” banner before they book?

Just because your airline won’t tell you about your flight’s performance doesn’t mean you can’t find out on your own. The best free way to figure this out is to go to

FlightRadar24(though

FlightAwaredoes this, too). Type in your flight number and look at its past week of history. How is it performing?

Here’s a Virgin Airlines flight from LHR to ATL. Pretty good! You could probably feel confident about booking it.

More comprehensive historical data is typicaly gatekept behind a paywall. FlightAware and FlightRadar24 provide this information, but if you want an even easier to read view, Flighty has it too. Our general advice is not to pay attention to flight history from more than ~60 days ago. It’s most useful for you to see the ultra-recent data, which can tell you a lot about how your flight is performing right now.

If you don’t have a choice about which flight to book, then this information can at least help you know what to expect. In any case, remember that your flight’s historical performance is a probability indicator rather than a guarantee. Shit can always hit the fan, and data can tell you if that’s more or less likely to happen.

On the day before your flight

There are two questions that really matter the day before your flight:

• Where is your plane right now?
• What will the weather be tomorrow?

Answering the first question is as easy as opening any of the flight tracking tools we’ve already mentioned. Check where your plane is now, what flights it has to complete before it reaches your airport, and whether or not it’s on time. (This only works if your airline has assigned a plane to your flight and made that information available to flight tracking apps. Thankfully, this is common.)

The day before you fly, you should only pay attention to whether there are any major delays. Airlines are good at making up time both in the air and on the ground, so if your airplane is only a few hours late to its next destination, you may be fine. But it’s a bad sign if your plane is severely (~10+ hours) behind schedule or if delays are compounding with every stop.

Then you should open your favorite weather app. If it’s going to be sunny, clear, and calm, weather will likely not be a factor. If the weather app shows anything else, your flight could be affected. The most concerning types of weather are snow, ice, strong winds, thunderstorms, and dense fog. Rain, unless it’s unusually intense or combined with other factors, does not tend to be a major problem on its own.

One more thing: if you booked your flight more than a month or two ago, it’s useful to do a quick check of the flight’s performance again. Has it been on-time over the past week or so?

On the day of your flight

It’s time to fly. Great. Will you be on time or will you have to spend another two hours mentally justifying the purchase of a 7-dollar water bottle? Just ask these questions:

• Is your plane going to arrive on time?
• Is the airport operating smoothly?

The weather is important, too, but you checked that yesterday. If you didn’t, check it now.

To see if your plane is going to land at your airport on time, open a flight tracking tool.

• If the plane is currently en route to your airport, it should have a mostly accurate ETA. To calculate when you will actually leave, add ~30-60m to the plane’s ETA if it’s a short-distance flight and/or a small plane. Add ~60-90m if it’s long-distance and/or a big plane (these are rough rules of thumb, not scientific laws). This accounts for the time it’ll take to disembark and re-embark with you on it. If this little math problem results in a departure that’s later than what your airline is telling you, expect to be late.

• If the plane is 2 or more stops away, it’s harder to confirm a delay—but you can still guess. If it’s on time? Great. If it’s <2h late to its next destination? Worrying, but your airline might be able to make some or all of that time up. If it’s >2h late? There’s a good chance you will be late, too.

This might feel like overkill. Why not just look at the departure board in the airport? The answer is that it won’t tell you. Many times, when a flight is going to be late, you can still hear people waiting at the gate saying things like: “Well, my airline app says it’s still on time.” But the question is not what the airline app or the departure board says. The question is—literally—where is the airplane right now?

A quick aside: When you get on the plane and your pilot says “we’re late, but we might be able to make up time in the air,” he might actually mean that they are going to fly faster. Planes are like cars, at least in the sense that the most fuel-efficient speed is not the fastest speed. Airlines will sometimes sacrifice fuel efficiency if they believe they have more to gain by making up lost time.

The final piece of the puzzle is analyzing the state of the airport. One rudimentary way you can do this is by simply looking at the departure board. Are there a lot of other delays? That might mean that the airport is not running well. A better way is to calculate the average departure delay of flights that have just taken off, but you probably don’t want to open an Excel sheet at gate C17. [0]

The other airport operations trick is knowing what the current ATC and FAA directives are.

You can see those here(United States only). You can even read about potential delays in advance:

And so, if you ever wanted to be way too nerdy about your flight and tell the airport bartender: “The people lined up at the gate don’t know the plane isn’t getting here for an hour.” Now you can.

A disclaimer

Most of these tactics help you figure out if your flight is more likely or less likely to be delayed. People are bad at internalizing probability—most of us prefer to think in definitive categories—so if you don’t think you can internalize it well, maybe don’t pay attention to this essay.

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[0] By the way, apps like Flighty (as of today, Flighty is the only real option) do this work, and more, for you so you don’t have to do it yourself. See what an actual Delta flight crew member has to say:

We don’t want this to come off as an ad, and have already acknowledged that one of us is sometimes paid by the people who make the app. But all of the information above is true, and it would be disingenuous to pretend that there isn’t any piece of software which makes this whole process easier. Leaving out a Flighty mention would make this essay less useful. So there you go.

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