Answered By AOPA
What is the definition of Class "B" airspace?
AOPA Staff Answer
The airspace from the surface to 10,000 ft Mean Sea Level (MSL) surrounding the nation's busiest airports in terms of IFR operations or passenger enplanements. The shape of each Class B airspace area is unique and consists of a surface area and two or more layers (some Class B airspace looks like an upside down wedding cake) it's designed to contain all published instrument procedures once an aircraft enters the airspace.