Plain English Meaning

The line, on a chart or in the air, where one type of airspace ends and another begins.

Full Definition

The defined edge — lateral or vertical — of a designated block of airspace, separating one classification or area from another (for example, the edge between Class B and Class E airspace, or the floor and ceiling of a Class C shelf).

Context Anchor

Seen on aviation charts, cockpit displays, and flight planning tools when checking whether a route enters, leaves, or stays near a particular airspace area.

Derivation

“Airspace” means the space in the air above the ground. “Boundary” comes from the idea of a bound or limit. Together, the term points to the limit of a defined area in the sky, not just a line on the .