Introduction to Aviation English

From ICAO language proficiency rating scale, Operational Level 4:

Pronunciation:

Pronunciation and stress influenced by the first language.

Structure:

Basic grammatical structures and sentence patterns used creatively and are usually well controlled.

Vocabulary:

Vocabulary range and accuracy sufficient to communicate effectively on common, concrete, and work related topics.

Fluency:

Produce stretches of language at an appropriate tempo.

Comprehension:

Comprehension mostly accurate on common, concrete, and work related topics

Interactions:

Responses immediate, appropriate, and informative. Initiate and maintain exchanges. Deal with apparent misunderstandings by checking, confirming, or clarifying.