When Flights Are Actually Cheapest: 59 Routes of Real Price Data

The short version

Across 59 routes, 34 hit their cheapest fares in August or September. That is 58% of everything we checked. July is the single most common peak month, topping out on 30 of 59 routes. So the pattern most travellers suspect holds up: fly the shoulder, skip the summer peak.

The widest gap on a well-covered route was New York to Paris. Cheapest in September at 355 USD. Peak in June at 942 USD. That is a 62% swing on the same route, drawn from 50 fare points across 9 months of data.

US departures: the autumn dip

For flights out of New York, LA, and Chicago, the cheap window lands in autumn. Cheapest months cluster in September, October, and November. Peak-to-trough gaps average 33.1% across the US routes we checked. Here are the clearest findings, limited to routes with five or more months of data.

Oslo departures: same shape, different currency

Oslo routes follow the same rhythm, with an average gap of 37.4%. August and September are the sweet spot for most European runs. Prices below are in NOK, so compare the percentages, not the numbers, against the US table.

Which month wins, across every route

The full dataset

All 59 routes, sorted by departure city then by price gap. "Data points" is how many real fares sat behind each route, and "Months" is how many calendar months those fares span. Avoid over-reading the thin rows: a route with one or two data points is a hint, not a finding. Trust the wide-coverage routes most, and click a destination to check live fares on that route.

How we did it

For each route we asked Travelpayouts for its forward price calendar, grouped the fares by calendar month, and took the lowest fare in each month. The cheapest and most expensive of those monthly lows give the spread. We then pulled a second, independent set of bookable fares per route and confirmed a real fare existed near each calendar low. Every one of the 59 routes passed that check.

The limits are worth repeating. This is cached affiliate-network fare data, not every carrier and fare class. It is one snapshot, taken on 10 July 2026. Routes with only a month or two of data are noisier, which is why we flag the sample size on every row. Re-running the pull is one script, so we can refresh this each season.

Book at the bottom of the curve

Found your route above? Fares move every day, so the month is the start, not the answer. Check the live price before you commit. Search your route on mondotickets and book when the number looks right.

Claude AI helped me with phrasing and proofreading in this article.