Sometime in our lives, everyone needs to find airline tickets cheap at the last minute. Unfortunately, too many times you can get charged far too much, simply because you're filing late. There are numerous ways to combat this, which I've described below.
Try to fly on Standby status. Basically, this means that if there is a seat remaining when the flight is set to leave, you get that seat for a heavily-reduced fare. This doesn't always work, of course, and you may have to try it for multiple flights before you finally get on one. Basically, put in a little extra effort to get the better price
Another way to find airline tickets cheap last minute is to use your American Airlines Miles (or whatever SkyMiles you have). Even if you have to get your flight at the last minute, the number of SkyMiles required to fly is generally unchanged.
If neither of the above two steps manage to work, do a search at expedia.com. They'll show you prices from all competing airlines, not just one specific company. When you can see any and all airlines that are available to fly on, it's far more likely you'll get a better price.
Be flexible!! If you're gonna fly at the last minute, and you want your airline tickets cheap, you're going to have to compromise on some things. Expand your search to include all hours of the day.
Further compromises may be necessary to ensure a cheap ticket at the last minute. Spread it out over a multiple day period. Or, be willing to take multiple connecting flights. These are sacrifices you might need to make to ensure that you get to your destination without wasting too much money. It's a trade-off: comfort for money. Good luck in your travels!!