ICAO LEVELS 4-6
ICAO divides the skill levels to be achieved into 6 categories from 1 to 6, level 6 being the highest level. The safety-relevant limit was set at level 4. This is the minimum level you need to achieve. Level 4 is also called the OPERATIONAL level. The next higher level is level 5 or the EXTENDED level, and finally there is level 6, which is restricted to EXPERTS (usually native speakers).
Basic Course: ICAO Level 4 Aviation English
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