OFA

OBJECT FREE AREA (OFA) See RUNWAY OBJECT FREE AREA.
OBSTACLE FREE ZONE (OFZ) - The OFZ is a three dimensional section of airspace that supports the transition of ground-to-airborne-aircraft operations (and vice versa).

Obstacle Free Area (OFA): A two dimensional ground area surrounding runways, taxiways, and taxilanes which is clear of objects except for objects whose location is fixed by function.