Making a platform

Hi allI need your help for making a platform. After doing a flatten, i've tried making a textured polygon with GMax, and putting it on the ground of the airport. The problem is the polygon appears onto the runway too!!So, that's the question: how can i make a platform and put it on the ground, and down the runway?Thanks a lot, and regards from SpainBill StonePD: Please, sorry if my english is not so good enough :-))