Definition
A block of airspace of defined vertical and lateral limits, assigned by air traffic control for the purpose of providing air traffic separation between aircraft, particularly between participating military aircraft and other IFR traffic.
Plain English
A chunk of sky with set boundaries that ATC hands to specific aircraft -- often the military -- to use for a while, so they stay clear of regular traffic.
Context Anchor
Seen in air traffic control procedures, special activity coordination, and AIM glossary material about how controllers manage airspace use.
Derivation
“Assigned” comes from the idea of marking something out for a particular use. That fits this aviation meaning: the airspace is not just generally available; air traffic control has designated it for a specific activity.
Why Pilots Care
Pilots need to recognize when they are inside ATC assigned airspace to comply with separation instructions and avoid conflicts with other traffic.
Intuition Check
Do not read “assigned” as meaning the airspace belongs to one pilot or group. Here it means air traffic control has designated that defined area for a particular activity and is managing separation around it.
Example Sentence 1
Center advised the flight to deviate twenty miles south to remain clear of ATC Assigned Airspace active for military refueling.
Example Sentence 2
The pilot remained inside the ATC assigned airspace to receive continuous radar vectoring around the restricted area.