Definition
Controlled airspace surrounding the nation's busiest airports, generally from the surface up to 10,000 feet MSL, shaped to the operational needs of the airport. Each Class B area is individually tailored and typically resembles an upside-down wedding cake. An ATC clearance is required to enter, and all aircraft within Class B receive separation services from ATC.
Plain English
The protected airspace built around the country's biggest, busiest airports. You cannot fly into it without first being cleared in by air traffic control, and once inside, controllers keep aircraft apart from each other.
Context Anchor
You will see Class B airspace areas on aviation charts and in rules about ATC clearance, radio contact, equipment, and speed near major airports.
Derivation
Class comes from a Latin word meaning a group or category. In this term, Class B means the airspace is in the B category of the U.S. airspace system, not that it is second-rate or less important.
Why Pilots Care
Entry requires ATC clearance; specific aircraft equipment like a transponder is mandatory; violations can result in certificate action.
Analogy
Picture an upside-down tiered wedding cake centered on the airport. The smallest tier sits on the ground at the airport itself, and each layer above it gets wider, with the top layer usually capping at 10,000 feet MSL.
Intuition Check
Do not read area as a flat circle on a map. A Class B airspace area is a three-dimensional block of air with sides, floors, and ceilings.
Example Sentence 1
Before transiting the Class B airspace area around Atlanta, the pilot called approach control and waited for the explicit clearance to enter.
Example Sentence 2
During the IFR flight, we descended into the Class B airspace area after receiving vectors from approach control.