The best time to book a flight

You've probably heard some version of "book on a Tuesday afternoon" or "flights are cheapest exactly 47 days out." Airlines have said publicly, more than once, that these specific claims don't reflect how their systems work — pricing is driven by inventory and demand forecasting (see how airline pricing actually works), not a calendar rule. That said, there are real, broad patterns in when fares tend to be lower — they're just wider and less precise than the viral advice suggests.

What actually holds up, broadly

• Domestic trips tend to have their lowest average fares somewhere in the range of one to four months before departure, with prices generally climbing as the date gets closer — but "generally" is doing real work in that sentence; plenty of routes don't follow it.
• International trips usually reward booking further out — often several months ahead — since long-haul inventory management works on a longer runway and last-minute fares are rarely a bargain.
• Peak travel periods (major holidays, school breaks) are the clearest exception to almost every rule: prices rise well in advance and rarely offer a late discount, because demand is high enough that airlines don't need to discount to fill the plane.
• Midweek departures (Tuesday/Wednesday) are modestly cheaper than weekend departures on many routes, simply because business and leisure demand both concentrate around weekends.

Why "the" best day to book doesn't exist

Every one of the patterns above is an average across thousands of routes and gets overwhelmed by route-specific reality: a route with only one or two competing airlines behaves completely differently from one with five carriers fighting for the same passengers. A new route just launched by a budget carrier can stay artificially cheap for months as a market-share play. A route with a capacity cut can get more expensive the further out you look, the opposite of the "usual" pattern. Generic booking-window advice is built from averages that don't know which of these situations your specific route is in.

What to do instead

Treat the broad patterns above as a rough starting point for when to start paying attention — not a specific day to pull the trigger. The reliable version of "buy at the right time" is watching your specific route's actual fare over the weeks leading up to your trip and buying when it genuinely dips, rather than trying to predict the dip in advance. That's the entire reason to track a fare instead of checking it once: the pattern that matters is the one on your route, not the average of every route. See getting the most out of price alerts for how to set that up so you don't have to watch it yourself.