How (and When) to Snag Cheap Fares

When is the best time to get the best value on airfare? It's the most-asked question travelers pose, and as spring break approaches, it helps to know that a recent study puts the average answer for a domestic trip at roughly seven weeks.

"Of course, a million caveats apply," says Jeff Klees, chief executive of CheapAir.com, an airfare-shopping engine. "If you're more flexible on your travel dates and time, you can get away with waiting closer to the time to travel."

In a study of "every possible trip combination" over 11,000 routes, CheapAir dissected more than 560 million fare-search records from 2012's 366 days. "For any given flight, the actual best time to buy might vary, depending on the market, the time of year, the day of week and other factors," Mr. Klees says.

But the short answer is 49 days before your departure for domestic flights, while the sweet spot for international flights is 81 days.

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Airlines will vary fare prices based on availability and preference. A typical flight from Los Angeles to Chicago could carry as many as 20 possible price points when the ticket is purchased. If the flight is wide open, all price points will be available.

As fewer seats become available, fares switch to higher levels and if the carrier sees flights filling briskly, it will spike the prices.

"You'll see crazy fares that are literally five times as much as what you would normally pay for a flight," Mr. Klees says.

Of course, if you want to sit in first or business class, plan to pay a premium for it no matter when you buy the ticket. Ditto if you want a seat in the first 10 rows of coach and, increasingly, if you want more leg room.

What's the priciest day to buy a ticket? The day before you fly, with the second worst, two days in advance and the No. 3 spot, three days ahead of time. That pattern sticks through 11 days out, underscoring the need to buy tickets as soon as you can.

The real trick to getting cheap fares is to travel during the so-called shoulder season, according to Anne Banas, executive editor ofSmarterTravel.com. The industry ranks travel into three seasons, high, low and shoulder. High, of course, is when the kids are out of school and the weather is great, or summer, while low is during the depths of winter, when fewer people are traveling, with the exception of the holidays.

"The best time to travel is in the middle of all that, spring and fall when prices are discounted, the weather is mostly decent and seasonal places and events are still open," she says.

Because spring break tends to spread out over a four- to six-week period in March and April, Ms. Banas says there are still deals to be found. It's Easter week, which this year falls on March 25-31, that's tricky.

Though she warns to watch for blackout dates on some packaged deals, she has seen offers to St. Croix in the U.S. Virgin Islands with $300 airfare credit if you book six nights or more and similar airfare credits for the Bahamas. The Atlantis, the biggest resort on Paradise Island in the Bahamas, has a $69-per-adult, per night deal plus other bonuses, though there are booking deadlines.

The best way to find an airfare deal that you consider a value is to track it closely. There are tools on websites such as Kayak.com, AirfareWatchdog.com and TripAdvisor.com that will do the legwork for you. And CheapAir has a price-drop payback offer that will pay the difference, as a travel voucher, if the price of your exact itinerary goes down.

Here's a quick primer on when to find the best deals.

Start early. Once you've got your plans in mind, even if you haven't decided if you can actually afford it, start tracking prices. That will give you a feel for the market conditions.

If you see a great ticket price, be ready to pounce on it. Many times price cuts are short-lived, like 24 to 48 hours.

If you're traveling during peak travel periods�and Easter week is one of them�give yourself more time. Those are likely to fill up fast with prices rising along the way. Best bet: Travel after Easter week.

As with any air travel, be flexible. Sunday and Friday flights are going to cost you more than a Tuesday or Wednesday. But during peak holiday travel like Thanksgiving, price will vary based on timing, Mr. Klees says. Last year, travelers flying Monday through Friday of the holiday week saved $114 over those who booked a Wednesday to Sunday flight.

Another caveat: CheapAir's recommendations come from an in-depth analysis of what happened last year. The industry is long known for its penchant to shift pricing gears at any moment, reacting to the economy, rising fuel prices and declining travel demands.

Write to Jennifer Waters at jennifer.waters@dowjones.com

—Jennifer Waters is a columnist for MarketWatch. Read more at marketwatch.com.