What should you state if you do not want a pilot to leave a frequency?

The most appropriate phrase to use when instructing a pilot not to leave a frequency is to say, "Remain on this frequency." This directive clearly communicates the expectation for the pilot to stay connected without ambiguity. The term "remain" conveys a sense of continuity and stability, ensuring the pilot is aware that their ongoing presence on the frequency is important for communication purposes.

Choosing alternative phrases such as “stay,” “hold,” or “continue” may not convey the same level of clarity or standard terminology commonly used in air traffic communications. While these expressions can imply the intent to keep communication open, "remain" is preferable, as it aligns with standard phraseology and helps maintain clear and effective communication between air traffic control and pilots.