Which certificate from the regulating authority signifies that one can operate an aircraft?

The certificate that signifies one can operate an aircraft is the Certificate of Airworthiness (C of A). This certification is crucial because it indicates that the aircraft meets the required safety standards and is deemed fit for flight. A C of A is issued after thorough inspections and assessments of the aircraft's design, maintenance, and operational capabilities, ensuring that it complies with aviation regulations set by the relevant authority.

The other options, while related to aviation, serve different purposes. A Certificate of Registration (C of R) pertains to the legal ownership of the aircraft rather than its airworthiness. An Air Operator Certificate (AOC) authorizes a company to operate commercial air services, but it does not certify the individual pilot's competency. Lastly, a Radio Telephony Station (RTS) license relates to communication capabilities rather than aircraft operation. Thus, the Certificate of Airworthiness is the appropriate designation for the ability to operate an aircraft.