All airline pilots and most of the professional pilots must have a good command of English language. Besides the airmanship and flying skills, English language is mandatory skill for an airline pilots. All technical manuals and information are shared in English language Proficiency of English language is verified by the means established by ICAO and EASA in either Testing service provider or Language testing body.
Minimum so-called Level of English language proficiency for operational use is international ICAO Level 4.