Three sites scour the Web for good deals and advise you on the best time to book. By Sean O'Neill August 31, 2006 Although Expedia, Travelocity and Orbitz shed considerable light on airline fares, they sometimes miss bargains. They also don't tell you whether you should buy your ticket now or later. Three lesser-known travel dot-coms address these issues and deserve a slot among your bookmarks. (The sites don't sell tickets themselves but send you to airline Web sites and online agencies for booking.) RELATED LINKS 25 Best Value Travel Sites Win the Bumping Game What You Need to Know About Air Travel One unique site is FareCompare.com, which collects fare data for domestic flights from the same sources the big three travel agencies use but displays it in a different way. You plug in your itinerary and the site reveals the day's lowest fares along with a chart of the recent trend in fares -- similar to a stock-price chart. Compare today's lowest fare for your route with the lowest average fares for, say, the past month. If today's fare is near the recent low, it's probably a good time to buy. The site updates its fares shortly after 10 a.m., 12:30 p.m. and 3 p.m. eastern time. For example, in July we sought round-trip tickets between Atlanta and San Francisco 30 days before the travel date. The lowest fare was $288. FareCompare said that the average advance-purchase fare for similar sales during the past few months was about $288, so this was a solid deal. If a fare doesn't stack up well, you may want to jump to Airfarewatchdog.com, which scours travel databases for domestic and international flights and then fetches fare specials that FareCompare and your favorite travel Web site might overlook. Use it when you're flexible enough to buy your tickets right now. (Your trip can be as little as three weeks or as long as a year away.) The site recently quoted, on 21 days' notice, a round-trip ticket from Los Angeles to Lexington, Ky., for $178 (before taxes), when fares during the previous month had averaged $487. We couldn't track down the $178 deal at the big three Web agencies or at FareCompare, but Airfarewatchdog spotted it at the Web travel agency CheapAir.com. Advertisement Later this year, when you want to know whether an even better deal is just around the corner, you'll be able to find the answer at Farecast.com. The site predicts whether fares on a route will go up or down in the near future, to help you decide when you should buy your ticket. To make its forecasts, the site analyzes past fare trends in airline databases and other factors affecting price. As of this writing, it only predicts fares between Boston and Seattle. But it plans to expand to cover routes between most major U.S. cities by year-end.