How is controlled airspace defined?

Controlled airspace is defined as an airspace of defined dimensions that provides service to Instrument Flight Rules (IFR) and certain Visual Flight Rules (VFR) flights. This definition is integral to understanding air traffic management and safety within the National Airspace System. Controlled airspace is designated to ensure that all aircraft operating within it are subject to specific air traffic control (ATC) separation and guidance, which is critical for maintaining safety and efficiency in busy airspace.

This categorization of airspace includes various classes (A, B, C, D, and E) and delineates the conditions under which different types of operations can occur, ensuring that controllers can effectively manage air traffic flow and mitigate the risks associated with flying in proximity to other aircraft. IFR flights are particularly dependent on controlled airspace, as they require clearances and adherence to ATC instructions to navigate safely, especially in congested areas.

The other options provided do not accurately reflect the definition of controlled airspace. For example, reserving airspace for military use, imposing specific restrictions on VFR flights, or designating airspace solely for uncontrolled flight lack the comprehensive characteristics that define controlled airspace.