People who have flexible dates get the best fares. There's no magic day to buy a fare, although there are cheaper days to fly--for domestic U.S. travel it's Tuesday and Wednesday, and for international trips it's usually Monday to Wednesday or Thursday.
You can often save hundreds of dollars by flying when the going is cheap, and sometimes it just requires tweaking dates by a few days. Indeed, Airfarewatchdog.com lists airfares based on the lowest possible price, assuming that you’re date-flexible, which is why people with specific travel dates often don't find the fares we list.
It's disappointing that Travelocity, Orbitz, Hotwire and Expedia have dumbed-down their flexible date search tools, in part because these searches place a lot of stress on their computer systems (searching for a needle in a haystack is more data-intensive than search just a specific date). But a few good options still exist, along with an interesting newcomer.
Here are some tools we use to find the cheapest flights. You can play too!
This online travel agency (OTA) site allows a 330-day search. 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, 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). First you have to sign up with your email. From the flights tab click on the "more search options" link under "find flights" and then choose 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.
No discussion of flexible date airfare search can exclude ITA Software’s Matrix Airfare Search function, but read why it shouldn’t be relied on as the Holy Grail.
The "pricegraph" feature isn't exactly a flexible date calendar but many people find it useful once they get the hang of how to use it.
Another favorite site has been online travel agency (OTA) Orbitz.com. They used to have a 30-day flexible date search but now it's just plus or minus 1 to 3 days.
Hotwire, also an OTA, works like Orbitz.com does. It, too, is powered by ITA Software. Again, just plus or minus 1-3 days.
This newish, under-the-radar site is a very cool airfare search product for many reasons. You enter a "to" and "from" airport and then a trip length such as "about two weeks" and you'll see a bar graph showing the fares for dates in that range.
Some airlines have good flexible date search tools as well.
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” choose a length of stay 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 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. It's right here.
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.