Almost everyone assumes a longer trip costs more. On most of the nonstop routes we price, it's the other way round: staying longer is often cheaper — the same flights, the same route, just a different return date.
Airlines don't price the number of nights you stay. They price the seat on each flight, and the two flights that make up a short weekend trip are the two most contested departures of the week. Extend past them and you're buying a Tuesday seat instead of a Sunday one.
Why nobody publishes this
Because measuring it properly is annoying. If you simply compare the cheapest fare on a route to the dearest, you get an enormous number — and it's wrong. That comparison quietly changes two things at once: the dates and the length of the trip. A three-night trip in October and a sixteen-night trip in September are not "the same trip on different dates."
So we hold the trip length fixed. For each route we take the best-sampled stay length, and only then look at what moving the dates does. That one correction cut our own headline figure roughly in half — which is exactly why it's worth doing.
What this doesn't say
- Not "always book longer". It's a tendency across routes, and yours may be one of the third that runs the other way. The point is that the length of your trip is a price lever, not a fixed input — and almost nobody treats it as one.
- Not a claim about the cheapest month of the year. We price a rolling window a few months ahead, so we can tell you what moves inside it, not what December will do in August.
- Not every stay length equally. We price the stay lengths people actually search — weekends and week-long trips get far more coverage than three-week ones, so the mix reflects our sampling, not travel in general.
How to use it
- Give the search a range of nights, not a number. "6 to 9 nights" prices every length in that band instead of assuming seven.
- Widen the window before you widen the budget. Dates move the price more than almost anything else you control.
- Check the length you'd rejected. If ten nights is possible, price it — on most routes that's the cheaper side of the trade.
- Search a flexible window from your airport — every date combination in your window, priced nonstop and ranked cheapest-first.
- See what your route usually costs — the typical price by month and by trip length, route by route.
Related: what the cheapest day of the week is worth, and why searching multiple weekends finds cheaper flights.
The cheapest version of your trip usually isn't the one you typed into the box. It's the same route, a few days over, and a stay that's longer than you assumed you could afford.