Last week, Hotwire unveiled improvements that make it easier for users to find the cheapest flights. Now, every time you search, the site will automatically check alternate airports and travel dates one or two days before or after your designated dates. It also lets you search for the cheapest days to fly within a 30-day window. Notably, all these functions work for international as well as domestic flights.
Other sites offer similar search tools, but most require you to take extra steps or perform multiple searches to figure out if an alternate airport or different travel dates would be cheaper than your initial travel plans. Kayak, for example, can look at both alternate airports and travel dates with one search. However, you have to use a variety of check boxes and pull-down menus to tell it what you want, and then the results are shown all jumbled together, rather than neatly separated like they are on Hotwire. Orbitz offers the same 30-day flexible date search tool as Hotwire, but Hotwire displays its results in a more easily scannable (to my eyes, anyway) format.
Overall, I'd say these improvements vault Hotwire to the front of the flexible search class.
(Editor's Note: SmarterTravel.com is a member of the TripAdvisor Media Network, an operating company of Expedia, Inc. Expedia, Inc. also owns Hotwire.)