Is this flight price actually good? What "26% below typical" means

When one of our alerts says a fare is 26% below typical, that sentence is doing precise work, and it is worth knowing exactly what it does and does not claim.

What it compares against

The comparison is against fares we have recorded for:

• the same route — not the region, not the country pair
• the same departure month — because seasonality is the largest single effect in most fares
• the same booking window — how far ahead of departure the fare was seen

That is the whole comparison set. If we have watched JFK to Lisbon for five weeks, "typical" means the median of what we saw for March departures booked roughly this far out. It does not mean the median of all transatlantic fares, or of that route across all seasons, or of what anyone else has published.

That comparison set also has to be large enough before we'll use it at all — see why we refuse to score 40% of the routes people ask us to watch for the threshold and why we set it there.

Why the narrower comparison is the honest one

A broader baseline makes almost every fare look like a deal, which is precisely why broader baselines are popular.

Compare a March fare against a full-year average and you will find it "below typical" whenever March happens to be cheap on that route — which tells you nothing about whether this particular March fare is good. Compare a fare booked three months out against fares booked three days out and everything looks like a bargain.

Both of those produce impressive percentages. Neither answers the question you actually asked, which is: should I book this now, or wait?

What the number does not tell you

It is not a prediction. We will say what a route has typically done; we will not tell you what it is going to do next. Nobody can, and a product that pretends otherwise is selling confidence rather than information.

It is also not a comparison against other sellers. We are not claiming this is the cheapest place to buy this fare — only that this fare, on this route, at this moment, sits well below what we have seen before.

And it is not a final total. The figure we quote is the lowest fare we have seen for those dates; bags and seat selection are extra. That does not distort the percentage, because both sides of the comparison are the same kind of number — today's lowest against the lowest fares we recorded before it. But a basic economy seat with a checked bag added can cost more than a slightly higher fare that includes one, so treat the price in the email as where yours starts — more on that in is basic economy actually cheaper?.

The percentage is computed, never written

One detail that matters more than it sounds: every number in the reasoning paragraph of our alerts is calculated by code before the sentence is written. We do use a language model to turn those figures into readable English, but it is handed a fixed set of numbers and every figure it produces is checked back against them before the email is allowed to send.

If a number appears that we did not compute, the sentence is thrown away and rewritten. If the rewrite fails too, you get a plainer sentence assembled from the data directly.

You should never see a number from us that nothing in our database supports. The full mechanics of the score itself — what it's built from, and where we draw the line at flights and nothing else — are on how the score works.