I didn't start renting at DFW until the consolidated rental facility was constructed, but if I remember correctly, there were some rental car agencies located in the airport terminal -- just outside the security entrance, where you find baggage claim and check-in.

I know there used to be a rental car facility on the north side of the airport, accessed by the Red Line of the DFW airport train. This was not very convenient from terminal 4E, as you would have to change trains to get to the Red Line (possibly 3E as well; now the Red Line serves the old 2W and 2E only).

Anyway, the DFW bus system of today is nice (albeit at a $3/day cost; or is it $5 now?) The buses run frequently, and the drivers are pleasant.

One time I wanted to reminisce, so I intentionally took the bus from the rental facility to the wrong terminal and then took the DFW airport train to my terminal.

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"It's as easy as 1, 2, C" -- Kelly, Married With Children