Hi Meshman --- well it looks like what I wanted to accomplish is not easily done. I guess the best thing for me to do is convert my project over to existing land mass, and forget the island idea. I want to put my time into building my new facility and airport and was hoping the land mass issue would be a minor part of the project.Hey, I sure appreciate all the info you guys passed along and now I have an appreciation as to what can and cannot be done easily in FSX relative to island building. Maybe some day, if it is possible, someone will devise a tool that can modify the primary underlying terrain mesh and make islands and other land mass changes an easy step. But for now, it is back to ADE (Airport Design Editor) and SBuilderX for some design on existing terrain.Thanks again -- and happy flying. Regards, Bob

Myself, I will always create a landclass layer in SBX for an island, as typically in FSX default landclass isn't defined very far from a default coastline. You can make a copy of your "hole" polygon, and set to airport background -- flatten and set your island elevation. It will be table-flat, but you can play with it more later if you want. Then create a second (smaller) polygon where you want your actual airport and again set it to airport background, but this time use -- masklandclass and excludeautogen. Of course if your island is small so the airport covers the whole thing just use the first airport background poly but use all three settings on it. Just make sure if you create either a hydro poly or an airport background poly with flatten set you must make sure you have altitude settings on the vertices. Note that this will make a visible island, but it isn't considered "hardened" until you place an apron, taxiway, or runway surface on it.scott s..