When to Book Flights to Get the Lowest Fares

As any procrastinator can attest, you'll usually pay a big premium by waiting until the last minute to book a flight. But you'll also pay more if you purchase your tickets too far in advance. So when should you book a flight to get the lowest fare?

To answer that question, airfare shopping engine CheapAir.com monitored fares for more than 4 million flights over a booking period ranging from 320 days in advance to one day in advance. Its researchers found that fares for domestic flights were lowest 54 days in advance. That's an average, though. There's actually a prime booking window between 104 days and 29 days before departure when fares for U.S. flights are the best, says Jeff Klee, CEO of CheapAir.com.

Those who booked before that window paid an average of $33 more per ticket, and those who booked after that period an average of $73 more per ticket, according to CheapAir.com. However, there are exceptions to these findings. Although you usually won't get a deal if you wait to book a flight 14 days or fewer in advance, you can save by purchasing tickets for some flights more than 54 days before departure.

When to book early

You need to book early to get the best fares on domestic flights to popular destinations during peak travel periods, flights during the holidays and on international flights, Klee says.

Flights to popular destinations. If you want to fly anywhere warm, you need to book sooner rather than later because flights will sell out, Klee says. For example, CheapAir.com found that the best time to buy tickets to Florida cities such as Ft. Lauderdale, Orlando and Pensacola - as well as some cities in Arizona and California - is 75 days in advance. For Las Vegas, it's 81 days in advance. And to get the best fares on flights to Hawaii, you need to book at least 87 days before departure - and even sooner if you plan to travel during Christmas, Klee says.

Flights during the holidays. Prices on flights around Thanksgiving and Christmas are notoriously high. So to nab fares when they're at their lowest, CheapAir.com found that you need to book in June - five months in advance of Thanksgiving flights and six months in advance of Christmas flights. If you can't make plans that far in advance, you can save by booking flights on the cheapest days to fly during the holidays, which are the holidays themselves, according to FareCompare.com.

International flights. For summer flights to Europe, you'll get the lowest fares by booking 319 days in advance, according to CheapAir.com. However, you'll save the most on trips to Europe by traveling during the fall or spring rather than in summer. A study by FareCompare.com found that prices on flights to Europe after May 16 rise 35% or more. Prices drop back to spring levels after August 23 and fall even more in late October, according to FareCompare.com. You'll also pay a premium for flights to the Caribbean before April 24, according to FareCompare.com.

You also should book early if you're traveling to a smaller city with limited service because flights will fill up quickly, Klee says. As the number of available seats dwindle, the fares rise.

More strategies to save

Monitor fares. Even though CheapAir.com found that there is a prime booking period for most flights, Klee says that fares are volatile. So the key to getting the best price for airline tickets is to check fares at least once a week, he says. This will help you spot price drops. When you see a deal, don't hesitate to buy your tickets because the price can change again quickly, Klee says. Signing up to receive fare alerts from Airfarewatchdog.com, CheapAir.com or Kayak.com will help you know when the price drops on flights you want to take.

Be flexible. According to FareCompare.com, you pay more for convenience, such as non-stop flights or flights on certain days and during certain time frames. Sometimes you can save a lot by booking flights with connections, or flights that are early in the morning or late at night. Also, flights on Tuesdays, Wednesdays and Saturdays tend to be cheaper, according to FareCompare.com. You can use a flexible search option on travel booking sites, such as the ones at Bing Travel or Kayak.com, to see which days have the best fares.

Check alternate airports. Most large cities have several airports nearby, and the difference in fares for flights into those various airports can be dramatic. Check prices on flights to all of the airports in or around the city you're visiting. If you're traveling to a midsize city with just one airport, look for cheaper flights to other nearby cities. If you were planning on renting a car anyway, driving an hour or so to get from the alternate airport to your final destination probably is worth it. If you weren't going to rent a car but will need to if you fly into an alternate airport, make sure the cost of the car rental and flight don't exceed the cost of flying directly to your destination.

Keep an eye on your fare after you buy because most airlines and online travel agencies will give you a rebate (usually in travel credits or vouchers) if your flight's price drops below what you paid. You can sign up on Yapta.com to receive alerts if the price falls on a flight you've booked. Be aware, though, that some airlines can charge hefty fees for re-booking your flight to get a lower fare. It's not worth it to make a change if the fee outweighs your rebate.

However, if you book a ticket through CheapAir.com, you can get a credit of up to $100 for future travel if the price of your ticket drops. You don't have to re-book your flight (and possibly incur fees) to take advantage of the site's Price Drop Payback credit.

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Cameron Huddleston is an online editor at Kiplinger's Personal Finance magazine. .