Which type of airspace requires pilots to communicate with air traffic control (ATC)?

Class C airspace requires pilots to communicate with air traffic control (ATC) as part of the airspace's operational requirements. This airspace is typically found around airports with a significant amount of air traffic, where ATC services are pivotal for facilitating safe and orderly operations. Pilots flying in Class C airspace must establish two-way radio communication with ATC before entering the airspace and must maintain that communication while operating within it.

Class D airspace also requires communication with ATC, but the key difference is that it is generally associated with airports that have a control tower but may not have the same level of traffic density or complexity as Class C. Class E airspace, on the other hand, does not mandate communication with ATC unless specifically required by the nature of the flight or operation, such as in some IFR conditions. Class G is uncontrolled airspace where no communication with ATC is required, allowing pilots complete freedom to operate without the need to contact air traffic services.

The requirements of Class C airspace emphasize the importance of communication in maintaining safety and coordination among different aircraft operating in areas with a higher volume of traffic.