Avis is located AT the airport. There is an "AirTrain" that runs to A, B, C ,terminals and the P3 stop. Avis is located at the P3 stop. Right where you get off. It is only a few minutes from arrival terminals. Look for signs for AirTran when you get off plane and head to baggage claim. It is free to ride the Airtrain.
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There is a train that takes you to the rental area. It takes a few minutes.
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