What phrase is used for a Conditional Clearance involving spacing (e.g. behind another aircraft)?

The phrase "BEHIND...behind" is specifically used in air traffic communication to issue a conditional clearance that involves the requirement for the pilot to maintain a specific spacing from another aircraft, typically for safety and operational efficiency. This phraseology is important as it clearly informs the pilot that they may proceed with their clearance while also advising them to maintain a specified distance from the aircraft they are following.

Using "BEHIND" emphasizes the conditional nature of the clearance, highlighting that the pilot's progression is contingent upon the positioning of the aircraft ahead. This terminology is part of standardized aviation phraseology, ensuring clarity and consistency in communications between air traffic controllers and pilots. Emphasis on such clear statements reduces the risk of misunderstandings that could arise during busy operations, enhancing safety within the airspace.

The other phrases presented do not capture the specific nature of maintaining separation in the same way. While they may be used in various contexts within aviation communication, they do not denote the specific condition of following another aircraft as effectively as "BEHIND...behind" does.