Definition
Airspace of defined vertical and lateral limits, assigned by Air Traffic Control, for the purpose of providing air traffic segregation between specified activities and other IFR air traffic.
Plain English
A block of airspace, with set boundaries and altitudes, that ATC sets aside so a particular activity (often military training) can take place without mixing with regular IFR traffic.
Context Anchor
You may see ATCAA in FAA glossary material, military flying discussions, or situations where ATC routes aircraft around an assigned activity area.
Why Pilots Care
Entering an active ATCAA without clearance can create conflicts with the assigned user and violate separation requirements.
Intuition Check
Do not assume ATCAA means ordinary public airspace that anyone can use freely. Here, “assigned” means ATC has set that block of airspace aside for a specific controlled purpose.
Example Sentence 1
Center advised us to expect a reroute around an active ATCAA being used for military refueling.
Example Sentence 2
ATC approved a direct routing after confirming the ATCAA was not in use.