Money

Here’s exactly when to buy plane tickets to get the best deals

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When planning a vacation, the less you spend on flights, the more you can put toward exploring your destination.

As part of its 2018 Airfare Study, CheapAir.com analyzed 917 million fares across 8,000 markets to determine the cheapest and most expensive days to book flights.

The ideal time for domestic flights: 70 days in advance. That's within what CheapAir.com calls the "prime booking window," which stretches from 21 to 121 days early to lock in the best prices. "Fares bounce around but frequently are available for within 5 percent of the lowest price," the study says.

The time of year you're aiming for matters as well. Here's how far out is ideal for each season:

Summer

Range: 14 to 160 days in advance
Best fare: 47 days in advance

Fall

Range: 21 to 100 days in advance
Best fare: 69 days in advance

Winter

Range: 21 to 110 days in advance
Best fare: 62 days in advance

Spring

Range: 46 to 122 days in advance
Best fare: 90 days in advance

For travelers wary of cutting it too close to their vacation, CheapAir.com says booking slightly earlier, 122 to 168 days in advance, will still offer plenty of good deals, but it will you cost an average of $20 more.

And while it's cheaper to fly out on a certain day, it makes no difference when you book your tickets, the study found.

It's also worth noting, though, that fares for individual trips are volatile, so it's best to keep an eye on the prices and jump on deals whenever you see them.

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