What type of airspace is controlled airspace?

Controlled airspace is defined as the airspace in which air traffic control (ATC) services are provided to manage the flow of air traffic and ensure safety. In this type of airspace, ATC may impose regulations to maintain safety and order, such as requiring pilots to communicate with ATC, adhere to specific altitude levels, or file flight plans before entering. This structure is designed to safely separate different types of aircraft, whether they are large commercial airliners or small general aviation planes.

In controlled airspace, pilots must comply with ATC instructions, which could involve altitude assignments, routing traffic, and other mandates to avoid collisions and ensure efficient traffic flow. The level and type of service provided can vary depending on the class of airspace, but the key feature is that ATC has the authority to regulate operations within it.

The other options do not accurately describe controlled airspace. For instance, controlled airspace is not closed to flight, nor does it exclusively require visual flight rules (VFR) or imply that there are no restrictions for pilots. Each of these options mischaracterizes the fundamental nature of controlled airspace and its interaction with aircraft operations.