There's a shuttle you have to take. It's free of charge. Most if not all car rentals require you to take a shuttle.
Hertz has several locations in Missouri & Kansas but the airport has the largest selection. 8130 Metcalf Ovpk KS is my favorite location though.
They're at the airport and if you're a gold member (free signup on their website) with a reservation you can just take any car you want and they'll check you out before you leave the lot
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