Checking bags will make it basically undoable unless your inbound flight is quite early or the AA flight is late. You will need to clear customs and retrieve your bags. That would take around 30 minutes. Then you would need to go follow the signs to the Airtran and take that to Terminal 8. From baggage claim to Terminal 8 on the Airtran would be at least another 10 more minutes. IIRC the cut off for checking bags at AA is one hour.