Which of the following is NOT an acceptable form of phraseology in air traffic control?

Nonstandard phraseology is considered NOT acceptable in air traffic control communications due to the need for clarity and precision in instructions. Air traffic control relies heavily on standardized phrasing to ensure that all pilots and controllers understand communications quickly and accurately, reducing the potential for misunderstandings that could lead to safety issues.

Standard phraseology is essential as it encompasses terms and phrases that are universally recognized and used within the aviation community. This standardization helps to ensure consistent communication, especially in high-stress situations or when language barriers might exist.

Formal directives refer to officially recognized commands or instructions that must be complied with, further emphasizing the importance of clarity and adherence to established procedures. Clear instructions, on the other hand, focus on delivering messages in a straightforward manner, which is also a vital aspect of effective communication in air traffic control.

The use of nonstandard phraseology, however, introduces ambiguity and could lead to confusion, which is why it is not acceptable in the professional environment of air traffic control.