What is the proper example of phraseology to request an aircraft at a different altitude, and the acceptable responses when acknowledged?

• A. Request AAL121 at one five thousand; respond with 'AAL121 at one five thousand (initials)' or 'AAL121, WILCO (initials)'
• B. Request AAL121 at one five thousand; respond with 'AAL121 at two five thousand'
• C. Request AAL121 at ten thousand; respond with 'AAL121, WILCO'
• D. Request AAL121 at five thousand; respond with 'AAL121, unable'

Answer: (A)

When changing an aircraft’s altitude, the communication should be clear and unambiguous: the controller or pilot states the target altitude, and the other party acknowledges in a way that confirms the instruction will be followed. The best example shows a straightforward request for a specific altitude and two acceptable acknowledgments. The request uses the aircraft’s call sign and the requested altitude, and the acknowledgment options give either a direct repeat of the assigned altitude (confirming exactly what was requested) or a Wilco (will comply) acknowledgment. The optional “initials” in parentheses reflect typical training or multi-voice environments where it’s useful to identify the transmitter.

So this pair demonstrates proper structure: stating the intended altitude change and then either repeating the altitude to confirm or saying Wilco to indicate compliance. The other options mix in an incorrect altitude, an incomplete acknowledgment, or an “unable” reply without a valid basis, which is why they aren’t the best fit.