I just noticed that you are going to Cancun from DFW. You may have to check your bags at terminal D, international gates. I don't know if AA will allow you to check your bags over at terminal A for international flights. If AA requires you to check your bags at D, then you can still go thru security at terminal A or B. DFW has free shuttle buses that are outside of security that can take you to other terminals. Go to http://www.dfwairport.com/terminallink/ for information on the shuttle, http://www.dfwairport.com/skylink/ for information on the secure Skylink service.