Which of the following best defines 'controlled airspace'?

Controlled airspace is defined as airspace in which air traffic control (ATC) services are provided to manage aircraft operations and ensure safety in busy flight paths. This includes services such as traffic separation, navigation assistance, and communication, which aid in the safe and efficient coordination of aircraft movements.

In controlled airspace, pilots must comply with ATC instructions, which helps maintain orderly traffic flow and reduces the risk of mid-air collisions, especially in areas with high air traffic density. The presence of ATC services also allows for better management of flight operations, including takeoffs and landings at airports.

The incorrect choices reflect other concepts related to airspace but do not accurately describe controlled airspace. For example, areas without restrictions or designated no-fly zones pertain to different categories of airspace management, while airspace solely reserved for military operations signifies a specific use that is separate from the broader air traffic control services typically offered in controlled airspace.