Standard phraseology is used when a standard expression exists for the intended radiotelephony message. Plain language is used when phraseology cannot convey what needs to be said. ICAO's Personnel Licensing FAQ makes both points together. Aviation English proficiency requirements do not reduce the need to use standard phraseology.

For an ATC learner, this distinction prevents two opposite mistakes: trying to improvise an expression where a prescribed one exists, and assuming that memorised expressions are enough to handle every unexpected exchange. This article explains the language-learning boundary, not the operational procedure for issuing a clearance.

What standard phraseology does

Standard phraseology provides established wording for situations covered by applicable procedures. The operational question is whether a standard expression has been specified for the message, not whether a speaker prefers a more conversational sentence. A language exercise cannot authorise a different wording in live operations.

ICAO explains that pilots and controllers should use standard phraseology in situations for which it has been specified. The precise phrase to use, readback requirements and local procedures must be checked in the applicable official operational publications and training material. This article deliberately does not offer a replacement phrase list or clearance templates.

What plain language does, and does not, mean

Plain language is needed when standard phraseology cannot serve the intended transmission. It is not a licence to be vague, to omit essential information or to invent a new procedure. In a non-routine exchange, a speaker may have to explain what is known, what is still uncertain and what information is being requested.

For a classroom exercise, imagine that someone says, “We noticed an unusual smell, but we have not identified its source.” The useful language skill is preserving the difference between a reported observation and an unconfirmed cause. A learner could summarise what is known and ask which detail remains unclear. This is an ATCBase-created language example, not an instruction for handling an aircraft event or a radio script.

The goal is understandable, accurate communication. Fluent-sounding speculation is not better than a careful statement that a cause is unknown. In actual operations, the applicable phraseology, procedures and circumstances determine what must be transmitted.

Why phraseology knowledge is not an ICAO language rating

ICAO distinguishes operational knowledge of standard phraseology from the assessment of plain-language proficiency. Its FAQ on technical questions in language tests says that testing phraseology cannot substitute for assessing plain language, while a language test cannot serve as a test of standard phraseology. A test prompt may contain phraseology as context without making technical knowledge the skill being rated.

The language rating scale addresses pronunciation, structure, vocabulary, fluency, comprehension and interactions in aviation work-related communication. A person may know a familiar clearance pattern yet struggle to explain an unfamiliar problem or understand a follow-up question. Conversely, a fluent general-English speaker still needs the separate operational training required to use prescribed phraseology correctly.

That is why “learn all the ATC words” and “speak conversationally” are both incomplete preparation plans. They address different parts of the work and must not be confused with a formal assessment result.

Two safe ways to practise the distinction

First, use an approved phraseology reference supplied by your training organisation to identify where prescribed wording applies. Compare your answer with that reference rather than with a blog or AI-generated phrase list. If a source is out of date or differs from local procedures, resolve the difference with your instructor.

Second, practise *explaining* a non-routine, work-related situation in ordinary English without pretending to issue an operational instruction. For example, have a partner give incomplete information. State what you understand, mark the missing part, then ask a focused clarification question. Swap roles and repeat with new information. The skill being practised is comprehension and interaction, not deciding an aircraft's next action.

For a structured listening, speaking and interaction routine, use our ATC ICAO English preparation guide. ATCBase ICAO English practice can offer additional conversation practice, but it is a simulation, not operational training or an ICAO-approved proficiency assessment.

The practical takeaway

Ask two separate questions: “Is there prescribed phraseology for this message?” and “Can I explain and understand what is not covered by a fixed expression?” The first belongs to applicable operational standards and instruction. The second is part of aviation English communication. Both matter, but neither replaces the other.

Sources and editorial scope

ICAO source checked 11 October 2026. The ICAO FAQ records a last update of 4 April 2018. Its published explanation is used for the distinction between phraseology and plain language; this article does not claim to state current local operating procedures. The classroom example and practice suggestions are original ATCBase material, not ICAO test questions or operational instructions.

  • ICAO Personnel Licensing FAQ: use of standard phraseology, resort to plain language, and the distinction between language tests and operational phraseology assessment