Which airspace generally requires explicit ATC clearance before entry?

• A. Class B
• B. Class C
• C. Class D
• D. Class E

Answer: (A)

The ability to enter different controlled airspaces depends on how tightly that airspace is managed. Class B airspace around major airports is the most restrictive, so ATC must explicitly authorize each aircraft before you enter. This explicit clearance is issued regardless of whether you’re flying VFR or IFR, and ATC will typically assign you a specific entry path, altitude, and sequencing. Pilots must be in two-way radio communication with ATC and usually have a functioning transponder with altitude reporting in this airspace. Because of this high level of control and traffic density, explicit permission to enter is the hallmark requirement. In other airspace, you generally must be in contact with ATC and follow their instructions to enter, but the formal pre-entry clearance isn’t always required in the same way, and uncontrolled airspace imposes no ATC clearance to enter.