Successful communication in aviation means effectively performing communicative tasks both in routine and non-routine/ unexpected operational situations. For reaching this goal you need to have:
1. a sufficient command of Standard Phraseology (click here to find out more),
2. a sufficient command of plain language (click here to find out more),
3. an awareness of language use (click here to find out more).
The minimum proficiency within these three areas of operational language might be called "Level X".