When the staff of Airfarewatchdog.com is researching airfares, we always start with a flexible travel date search. But a lot has changed in the last few weeks, in part thanks to new D.O.T. regulations requiring full disclosure of mandatory taxes and fees in all airfare advertising and online search.
Travelers can often save money if they adjust their travel dates to take advantage of the lowest possible fare between any two cities. Oddly, however, statistics show that most airfare buyers ignore flexible searches. That's probably because the majority of travelers, such as those going on a cruise or attending a meeting or wedding, need to travel on set dates. But we believe that it's also because many airfare buyers simply aren't aware that flexible search options exist, or don't appreciate the savings that can be achieved by being flexible. You can save hundreds of dollars simply by going a day or two earlier or later than you originally planned, or by postponing your trip for a month or two (Aunt Freda probably will be just as happy to see you in March as in May).
Here are your options when performing a flexible date fare search:
Update: Travelocity used to have a very useful 330-day flexible travel date search. As of late January, 2012, however, in order to comply with U.S. Department of Transportation rules concerning tax-included airfare advertising, Travelocity disabled this function. They do still offer a plus or minus 1 to 3 day flexible search option. Rumor has it that they're working on redesigning their flexible search options. Stay tuned.
For now, Cheapair is the only game in town when it comes to searching up to 330 days ahead. However, it only returns fares on routes within North America, not international ones. In order to comply with D.O.T. rules, the site currently adds "estimated" taxes and fees to all fares. It's an interesting workaround but not entirely accurate (it tends to overstate the final fare you'll pay) but it's still very useful.
Soon after the new D.O.T. rules were put into effect, Orbitz began hiding its 30-day flexible search function to some users. We have no idea why (but the link above should bring you to it, at least as of this writing). Excluded are fares on Southwest Airlines, Allegiant and several international carriers, such as Ryanair. Look for the "Flexible dates" link in the lower left corner of the blue box, then choose one of the three options. Domestic and international destinations are supported. You can also perform fare searches between non-US origins and destinations. Here's our User Guide for a Flexible Dates Search on Orbitz.com.
Owned by Orbitz, it uses the same software (from ITASoftware.com, see below) and comes up with exactly the same fares.
Known for its "know the airline only after you buy" discount fares, you can also buy tickets the old fashioned way here. As with Orbitz and Cheaptickets, you can view flexible travel dates only in 30 day increments of your choice. The advantage is that the same search will also show you Hotwire's consolidator fares, which are often great deals when you don't have the usual 7 to 21 day advance purchase. Check out our User Guide for a Flexible Dates Search on Hotwire.
Now owned by the Google juggernaught, his company provides the software that Orbitz and Cheaptickets (and many other sites) run on. You can't book fares on the site--it's for informational purposes only--but many people find it easier to do a flexible date search here than on the third-party sites that use it. It's free to use, and you can register if you wish, but it's not required. As you might expect, no Southwest fares are included. Using the flexible search is easy: click on "Looking for airfares?" and then select a month-long search using the radio button in the upper right corner; type in the from and to cities, and choose an outbound date starting, generally, 7 to 14 days from today; hit go. It's easy to search the next 30-day period and the next until you get an idea of fares. You can also search nearby alternate airports. Click on "details" to find out more about the itinerary.
Kayak used to only show plus/minus 1 to 3 day flexible search in real time results, or you could see a month-long view based on what other consumers found in the past 48 hours, which was hardly useful since fares change so often. Now, however, it has a real-time month-long flexible date search function and it's one of the best.
Individual Airline Sites
Some individual airline sites also provide a flexible date search option. Southwest Airlines offers a low fare calendar that now includes all mandatory fees and taxes in the initial display results and shows a month's worth of data at a glance. AerLingus.com also does a good job showing flexible dates. United.com now shows plus or minus 5 days in its flexible search.