What phraseology should be used to indicate to an aircraft that it has been radar-identified?

The phraseology "Cherokee Six Four Mike, radar contact" is used to indicate to an aircraft that it has been radar-identified. This phrase is specifically designed for communication clarity and precision in air traffic control. By stating "radar contact," the controller is informing the pilot that the aircraft's position has been positively identified on radar, which is crucial for ensuring situational awareness and safety.

This phrase confirms to the pilot that their aircraft is being tracked and that they are in a radar environment, allowing for effective communication of instructions and position reporting. The use of the specific aircraft identifier, "Cherokee Six Four Mike," further personalizes the communication, fostering a clear line of communication between the controller and the pilot.

In contrast, other options do not convey the radar identification status. "Radar loss" indicates a lack of radar contact, while "cleared for takeoff" pertains to departure clearance and does not confirm radar tracking. "Proceed on assigned route" indicates specific instructions but does not confirm that radar identification has been achieved. Thus, the correct choice is the phrase that explicitly indicates the radar contact status.