For the Cheapest and Fastest Air Fares, Make Your Connection Online

In 36 hours, you need to be in Chicago and you don't have a plane ticket yet.

Maybe it's an unexpected business trip or a family emergency -- or you simply crave authentic Deep Dish Pizza -- but when you need to fly at the last minute, using the Internet to book your flight can make things a lot easier and cheaper. But with dozens and dozens of online travel sites out there, ensuring that you get the best last-minute deal on a domestic flight can be a time-consuming and complicated process.

Last year, more than 26 million people bought airline tickets online -- more than 15% of airline revenues come from the Web, according to Forrester Research. And while the Web may make shopping for airfares a snap, there's no one-stop shop around that can guarantee the lowest prices. And so online travel shoppers scour the Web, visiting an average of 3.5 Web sites before they purchase their tickets.

Here are the steps you can take to get the best deal in a hurry.

Step One: Take the Broad View

In order to keep supply in line with reduced demand, airlines rely on yield management, constantly adjusting their fares on a moment-to-moment basis. Because of this, a round-trip flight between Miami and Dallas can cost $500 one day and $300 the next. The first thing you need to do is get a ballpark figure for how much that fare should cost.

The best way to get the big-picture view on fares is by checking one of the big three online travel companies, Expedia(EXPD), Travelocity(TVLY) or Orbitz. For the most part, the flights listed on all three sites are largely the same, culled from one of the four global distribution systems, or GDS, where the airlines publish their fares.