It's been a long time since I last wrote about how to do a flexible date airfare search and a lot has changed. The changes were the result, mostly, of new requirements stating that all mandatory taxes and government fees be included in airfare searches. But other factors were at work. Flexible date searches place extra strain on website resources, since more data must be crunched compared to specific date searches, so websites aren't particularly eager to promote them.
Why do a flexible date search in the first place? While many if not most people have specific travel dates in mind (for a wedding, meeting, school vacation, etc.) there are always consumers who will fly whenever it's cheap. It's these bargain hunters for whom flexible travel date airfare search is ideal. You can often save hundreds of dollars or pounds by flying when the going is cheap and sometimes this just requires tweaking dates by a few days. Indeed, Airfarewatchdog.com lists airfares based on the lowest possible price, assuming that you're date-flexbile.
My old "go to" flexible date website used to be Travelocity.com, which showed a flexible travel date fare calendar option with up to 330 days of travel. That feature is gone, clearly a victim of the new tax-inclusive regulations. Now Travelocity only allows a plus/minus one, two, or three day search.
But other fare search sites still allow flexible search options over at least 30 days.
Cheapair.com
This online travel agency (OTA) site allows a 330-day search, assuming that the fare you choose is available for sale any month of the year. It only works on some domestic U.S. routes and doesn't include Southwest, Allegiant and other airlines that sell fares only on their own websites. To use this feature, enter an origin and destination and check the "My dates are flexible" option. Although it's convenient and easy to use, Cheapair charges a $9.95 booking fee. As far as I know, it's the only site that still shows searches over 330 days. (By the way, if you're wondering why only 330 days, that's the maximum period over which major domestic U.S. airlines such as Delta, US Air, American, and United publish airfares. Other airlines, such as JetBlue and Southwest, publish fares over shorter time periods).
Kayak.com
Kayak, a meta-search travel site rather than an OTA (the difference between meta search and OTA is explained here, has a robust flexible date search, powered by ITA Software (see below). From the flights tab choose "make my dates flexible" and then +/- 1-3 days, weekends, or Flex month. If choosing flex month, specify a departure date and a trip length, either a single number of nights or a range of up to any seven days (such as 6-8 or 18-25). As is the case with Cheapair, you won't find Southwest, Allegiant, or Ryanair, but you will find a wide range of destinations, domestic and international. Once in a while, however, you'll click through on fare found via flexible search and find that it's not available. That's just the nature of the beast. And you may not find the best possible routings, since airlines apparently don't share their entire inventories with third-party sites.
ITA Software Matrix Search
No discussion of flexible date airfare search can exclude ITA Software's Matrix Airfare Search function, but read why it misses some low fares and how to use it.
Orbitz.com
Another favorite site has been online travel agency (OTA) Orbitz.com. But like Travelocity, Orbitz made some changes. You'll no longer find a link from the home page to Orbitz's 30-day flexible search feature (this feature allows you to search for the lowest fare between any two destinations over any 30 day period you choose, up to 330 days ahead).
However, the feature still exists. It's hidden here.
From this page you can choose to search for a weekend trip, a +/- one-to-three day trip, or a trip lasting between 2 and 16 days beginning and ending within any 30-day period. This feature works for most airlines (with the notable exception of Southwest, Allegiant Ryanair, and several others that only sell flights on their own websites), and most routes, whether domestic or international. Like Kayak.com, Orbitz is powered by ITA Software. But unlike Kayak, Orbitz is a travel agency, not a meta-search site. (Kayak will sometimes send you to an OTA rather than to an airline site directly if there's a lower fare option on the OTA).
Hotwire.com
Hotwire, also an OTA, works almost exactly like Orbitz.com does. It, too, is powered by ITA Software.
Then there are the airline websites. As with the meta-searchers and OTA's, many airline sites are powered by ITA. But only two -- United and Southwest -- have powerful flexible date searches.
United.com
One of the positive changes United made when it combined the Continental website with its own was to introduce an excellent flexible date function. From the home page "Flight" tab choose a calendar start date, a length of trip, click on "My dates are flexible" and search. Use the blue forward arrow to the right of the calendar search through United's entire schedule over 330 days, month by month. Easy.
Looking at the major U.S. legacy carriers, in contrast, Delta.com only allows a +/- 1-3 day search when you choose "My dates are flexible" from its home page. US Airways doesn't have a flexible option at all; and American used to have a 30-day flexible date search but got rid of it.
Among the smaller U.S. airlines, JetBlue doesn't have a true flexible date search, but once you enter your route and dates, you can forward-arrow week-by-week from both your original departure and arrival dates to find alternate fares. Virgin America offers the same functionality. It's a bit time-consuming and clumsy, but better than what's offered by USAir and others.
Southwest.com
Southwest doesn't list its fares on meta-search or OTA sites, but it does have an excellent flexible date search feature. As the case with other sites mentioned here, Southwest.com doesn't scream this fact from its homepage. To find the "Shortcut" Low Fare Calendar takes some work, unless you know where it is.
But it's simple to use. Choose a departure and arrival city and a departure and arrival month and you're all set.
Over in Europe, easyJet.com has a simple and effective flexible date tool. Just click on the "Flexible on dates" box to use it. Ryanair.com has one too, similar to the JetBlue model. Interestingly, the "Flexible dates" button is pre-checked, suggesting that Ryanair prefers that you be flexible to find its lowest fares. AerLingus.com also defaults to flexible dates, searching over a two-week period for both departure and return. Britishairways.com automatically shows a seven-day flexible date range and provides previous week and next day arrows to further search.