ICAO English Levels 4, 5 and 6 Explained

Written and reviewed by About us, airline pilot and certified aviation English examiner · Updated 20 September 2026 · Read in: English Italiano Español Português Français العربية

The six ICAO language descriptors

Examiners assess pronunciation, structure, vocabulary, fluency, comprehension and interaction. Each area receives a level. The overall result is not an average: the lowest individual descriptor determines the final ICAO level.

ICAO Level 4: Operational

Level 4 is the minimum operational standard for international radiotelephony. A Level 4 speaker can communicate effectively in routine and unexpected situations, although errors, hesitation or accent may sometimes be noticeable. Communication must remain intelligible and misunderstandings must be resolved successfully.

ICAO Level 5: Extended

Level 5 reflects more consistent control of language. Vocabulary and structure are broader, speech is generally smooth and comprehension remains strong across different accents and operational situations. Occasional mistakes may occur without interfering with effective communication.

ICAO Level 6: Expert

Level 6 demonstrates flexible, precise and natural communication across familiar and unfamiliar situations. It does not require a particular native accent. The standard concerns intelligibility, control, comprehension and interaction—not nationality.