Obstacle-free zone
The obstacle-free zone (OFZ) is a 3D volume of airspace below 150 feet (46 m), above the established airport elevation which protects for the transition of aircraft to and from the runway. The Obstacle Free Zone (OFZ) clearing standard precludes taxiing and parked airplanes and object penetrations, except for frangible navigation aid (NAVAID) locations that are fixed by function.