Radiotelephony
Pilot-to-ATC standardized communication.
Radiotelephony is the standardized phraseology used for pilot-to-ATC and ATC-to-pilot voice communications in civil aviation. Radiotelephony is defined in ICAO Doc 4444 (Procedures for Air Navigation Services — Air Traffic Management) and ICAO Annex 10 Volume II, and is the foundation of aviation English.
Standard radiotelephony covers routine situations: aircraft identification, frequency changes, altitude assignments, heading changes, taxi instructions, takeoff and landing clearances, holding instructions, traffic advisories. These are the situations where pilots and controllers use standard phraseology.
However, ICAO Level 4 also assesses plain-language proficiency — the ability to communicate effectively in non-routine situations where standard phraseology is insufficient (medical emergencies, weather diversions, equipment failures, unfamiliar airspace). Plain-language proficiency is what distinguishes Level 4 from Level 3.