This advisory circular (AC) provides a model zoning ordinance to be used as a guide to control the height of objects around airports. It is based on the obstruction surfaces described in Subpart C of Federal Aviation Regulations (FAR) Part 77, Objects Affecting Navigable Airspace, current edition. It should be recognized, however, that not all obstructions (objects whose height exceeds an obstruction surface)
are a hazard to air navigation.