Visit aa.com and click on the "AAdvantage Redeem Miles" box in the "Book Flights" tab on the main page.
Fill out the required information on this page, including departure and arrival locations and dates and whether your dates are flexible or exact, then click on "Go." This will open a page displaying the cost in miles of each flight you have requested. If you have stated that your dates are flexible, you will see a calendar displaying the cost in miles of flights on days surrounding the dates you chose.
Enter the dates (if you previously chose that your dates are flexible) and class level for each flight. Your options for classes, as of August 2010, include Economy MileSAAver (12,500 miles each way), Economy AAnytime (25,000 miles each way), Business/First MileSAAver (25,000 miles each way), Business/First AAnytime (50,000 miles each way), First MileSAAver (32,500 miles each way) and First AAnytime (65,000 miles each way). However, some levels might not be available on your selected dates.
Click "Continue" when you have finished selecting dates and classes. This will take you to a page that allows you to choose your specific flight if more than one is available that meets your criteria. Select your departure and return (if applicable) flights, then enter your AAdvantage account number and password in the corresponding fields at the bottom of the page. Afterwards, click "Log In."
Fill in your required passenger details on the page that appears, then click "Continue." This will bring up a page displaying details for this booking, including the flight details and the total number of miles required.
Click "Purchase" at the bottom of the page to complete your booking.American Airlines offers AAdvantage miles as an incentive to remain loyal to its brand. You can earn these miles by flying on American Airlines flights, purchasing things through American Airlines' online shopping program, dining and using a registered card at specific restaurants, signing up for an American Airlines credit card, winning contests or completing special offers. As of August 2010, a one-way flight within the continental United States cost a minimum of 12,500 American Airlines AAdvantage miles.