Finding the best flight deals is a bit of an art form, but there’s also some science — or at least economics — involved. There are only two definitive rules: Flights open for booking about a year in advance, and the airfare will change often between then and takeoff. So, as a general rule of thumb, you’ll want to book plane tickets well in advance of your trip, as prices spike sharply in the days preceding the flight, taking advantage of any last-minute travelers who have no choice but to pay up.
But there are many variables that impact the dynamic pricing patterns of plane tickets, including the destination and time of year. In some cases, you can book just a couple of weeks in advance (domestic trips in the fall), while in others, you’re better off booking months ahead (such as a trip over a big travel holiday, when demand is high).