Plain English Meaning

A block of sky that controllers temporarily set aside so a particular activity — usually military operations — can take place without other aircraft passing through it.

Full 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. An ATCAA is typically established to contain activities such as military training or aerial refueling that require non-standard separation from other traffic.

Context Anchor

Seen in high-altitude routing discussions, especially where RNAV routes must be planned around airspace used for special activity.

Derivation

The name is descriptive: airspace that assigns for a use. 'Assigned' here means handed for a defined purpose and time, not permanently designated.