Airspace

Controlled Airspace is airspace of defined dimensions within which all aircrafts are controlled.

UK Airspace is divided into classes, labelled from A to G. (Although there is currently no class B airspace in use.)

Classes A, B, C, D and E are controlled airspace.

Classes F and G are uncontrolled airspace.

Controlled airspace is subject to restrictions regarding entry and compliance with Air Traffic Control (ATC) instructions.

A Control Area (CTA) established at the confluence of ATS routes in the vicinity of one or more major aerodromes is known as a Terminal Control Area (TMA).

The part of an airspace of defined dimensions above a defined area where flights are not allowed, is called the terminal control area.

Prohibited Zone are areas over which flight of aircraft is not allowed under any circumstances. These zones are typically established for security or safety reasons.

A Restricted Zone is an area where flights are subject to certain restrictions. Aircraft may fly through restricted zones, but only with explicit permission from the controlling authority, and often under specific conditions.