a defined volume of airspace within which, variously, activities dangerous to the flight of aircraft may be conducted at specified times (a ‘danger area’); or such airspace situated above the land areas or territorial waters of a State, within which the flight of aircraft is restricted in accordance with certain specified conditions (a ‘ restricted area ’); or airspace situated above the land areas or territorial waters of a State, within which the flight of aircraft is prohibited (a ‘ prohibited area ’).
EUROCONTROL (2010) Draft EUROCONTROL Specification for harmonized Rules for Operational Air Traffic (OAT) under Instrument Flight Rules (IFR) inside controlled Airspace of the ECAC Area (EUROAT), Ed. 1.2
COMMISSION REGULATION (EC) No 2150/2005, of 23 December 2005 laying down common rules for the flexible use of airspace
In the context of SESAR, this term is often referred to as "airspace reservation/restriction" (ARES).