Start with the usual price

The question isn't "is this cheap?" but "is this cheap for this route, on these dates, for this length of trip?" A return to Bali in the school holidays and the same trip in February are different products, and so are a weekend and three weeks away.

So compare like with like: the same route, the same time of year and a similar trip length. Around busy holidays, compare with the weeks either side, or a peak fare will look like a bargain next to an even higher one.

Where to see price history

Google Flights shows whether the prices for your search are low, typical or high, with a chart of how they've moved, and can track a route for you. Many booking sites and apps offer similar price tracking for a route you've already chosen.

That works well when you know where and when you're going. If you're flexible, tracking one route at a time misses most of the drops, which is the gap deal alerts fill.

What price predictors can and can't do

A flight price predictor estimates whether a fare will rise or fall, from how prices on that route have moved before: the season, how far ahead you are, and demand. It can tell you the likely direction. It can't know about a sale, a mistake fare or a new route before it happens, and no tool knows tomorrow's price.

Treat a prediction as a nudge, not a promise. The surer signal is a fare that's already well below what the trip usually costs.

How much below usual is a good fare?

FarePop's rule of thumb, from its savings methodology: at least 20% below the usual price for those dates is a good fare, and at least 25% is a deal. Drops that size don't come along often for a given route, and they don't last.

Count the whole cost before you decide. Bags, seats and a distant airport can wipe out a saving, so compare the trip you'll actually take.

Book now or wait?

  • Book now when a fare is well below its usual price for your dates and the trip works. Waiting for a little more usually loses the fare.
  • Wait when the price is typical or high, your dates are flexible and you're months out.
  • Know your safety net. For flights to, from or within the US booked at least a week ahead, US rules let you cancel within 24 hours without penalty (or hold the fare). Elsewhere, check the fare conditions before you pay.