Thinks to do depend alot on the time you arrive and depart. Considering AA leaves sometime around noon you would arrive early morning on a sat. I will assume. 3 hour check in really leaves you around 4 hours. Downtown in either direction Dallas or FW will take about 45min each way again depending on traffic. Your best bet would be to stow up in the Admrials club, have a few snacks and bring your laptop if you want, free wireless in house.
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I read it on the internet so it must be true.