X-Plane World Editor Scenery Packs always produce this error (which returns zero search results in Google as of June 2013): BE ADVISED illegal DSF polygon type make sure your extension is .fac, .for or .bch (io_dsf.cpp line 553) steps to reproduce: 1. Open WED (I have used 1.1 and 1.2). 2. Click "NEW SCENERY PACKAGE". 3. Rename "Untitled 1" to "31qz" (Xplane returns no results for this code, so it shouldn't interfere with anything). 4. Click "OPEN SCENERY PACKAGE". 5. Select "Airport > Create Airport". 6. Change name from "unnamed entity" to "atlanticapt" and ICAO ID to "31qz". 7. Select runway tool, draw runway (for this test, I drew it over the Atlantic Ocean off the coast of Georgia so I know the exact elevation above sea level and know that there is currently no scenery or airport there). 8. Change Latitude, Longitude of the center to 32N, -80W, length to 2000ft, heading to 0, width to 150. 9. Draw taxiway next to runway. 10. Draw boundary around runway and taxiway. 11. Save, export apt.dat (creating new folder, "Earth Nav Data" inside "31qz"). 12. Open X-plane (9.67), verify that runway and taxiway exist. 13. Close X-Plane. In WED, select forest. Inside airport boundary, draw rectangle. 14. Save, and select "export scenery pack". A dsf file is created in "31qz\Earth Nav Data\+30-080". 15. Open X-Plane. X-Plane throws the above error and crashes. To date, I have not found any combination of objects in World Editor that will produce a scenery pack that does not cause this error.