Plain English Meaning

A part of the sky where the controller cannot see your aircraft on radar. Instead of watching you on a screen, the controller relies on what you tell them about where you are, your altitude, and what time you crossed certain points.

Full Definition

An airspace area or operating environment in which air traffic control (ATC) does not have radar coverage of the aircraft, so separation, traffic management, and clearances are based on pilot position reports, time, altitude, and published procedures rather than on a controller's radar display.

Context Anchor

Seen in instrument procedure discussions, especially when flying or in where radar coverage is or unavailable.