What is the correct phraseology for informing an aircraft that radar contact has been lost?

Informing an aircraft that radar contact has been lost requires precise and clear communication to ensure the pilot understands the situation and can take appropriate actions. The correct phraseology, "Radar contact lost; alternative instructions," effectively conveys the loss of radar contact while also indicating to the pilot that there will be further instruction provided. This is critical in ensuring situational awareness and maintaining safety.

The phrase emphasizes that, even though radar contact is no longer available, there are still procedures and next steps that the pilot can follow. This helps to mitigate confusion and ensures the pilot is aware that they should be prepared for instructions, securing their attention to promptly respond and act.

Other options may lack clarity or proper procedure. They might either fail to ask for the necessary position from the pilot or could imply a continuation of tracking which might not be feasible without reliable radar contact. Thus, using clear and unambiguous phraseology is essential in air traffic communications, particularly in situations with potential safety implications like losing radar contact.