For any route, there can be a wide variety of possible airfares. However, you can get a sense of what a good deal is on your itinerary by checking the lowest published fare at Travelocity, Expedia, or Orbitz, three of the largest online travel agencies. You can't guarantee that seats will be available at the lowest fare on the days you wish to travel, and you might find better deals with Web-only or last-minute specials. But the lowest published fare can be a useful benchmark to know as you continue your search for a great deal.
You can search for the lowest published fare on some popular routes with the tool below. Or, if your city is not listed, visit Travelocity. Enter your departure and destination cities or airport codes and choose "Flexible Dates." After you see the lowest published fare, click on "Rules" to find out available travel dates, booking deadlines, and other restrictions. Expedia and Orbitz offer similar tools.