If you decide you want to remove a scenery area from the Flight Simulator world, these are the steps to do so:
Remove the scenery from the scenery configuration file from FS: In FS (FS98, 2K, 2K2), go to the World menu, and select Scenery Library. In FS2K4, the Scenery Library button is available in the Start screen in the "Settings" tab. Find your scenery and click "Delete Area".
Remove the scenery from your hard disk (optional): In Windows Explorer, navigate to the folder where you exported the scenery (if you don't know where this is, in the scenery in FSSC, select File->Export Scenery Wizard. The "Base Location" field is the place where the BGL files are located. Unless you installed scenery to an existing location, it is safe to delete the entire folder containing your scenery. However, if you exported to a folder that already has existing files, you will have to manually find your scenery files and delete them individually. In the "Scenery" subfolder, these will be the files that have your airport name in them. It is best to leave the "Texture" subfolder alone in this case unless you know exactly what texture files your scenery used.