The EUROCONTROL Concept of the Flexible Use of Airspace (FUA) is that:
an ASM concept currently applied in the ECAC area and based on the fundamental principle that airspace should no longer be designated as either pure civil or military airspace, but rather be considered as one continuum in which all airspace user requirements have to be accommodated
an airspace management concept applied in the European Civil Aviation Conference area on the basis of the “Airspace management handbook for the application of the concept of the flexible use of airspace” issued by Eurocontrol
EUROCONTROL also defines Special Use Airspace (SUA) as:
Airspace of defined dimensions identified by an area on the surface of the earth wherein activities must be confined because of their nature and/or wherein limitations may be imposed upon aircraft operations that are not a part of those activities.
Question: what is the relationship exists between SUA and FUA? Can they be considered as the same thing? Is SUA a special type of FUA or vice-versa? What is the difference essentially?