In 2003 ICAO introduced strengthened language proficiency requirements for all pilots ATC controllers and aeronautical station operators who are now required to demonstrate a minimum English language proficiency at ICAO Level 4 Operational English language proficiency is a vital safety issue While Standard Phraseology is the most important factor of effective verbal communication it is recognized that there may be circumstances where plain language communications in English become necessary Difficulties in plain language communications between ATC and flight crews have often contributed to serious incidents and accidents In recognition of this ICAO has introduced the new focus on Plain English which is necessary inflight operations when Standard Phraseology is not enough This is particularly relevant in non routine or emergency situations In 2003 ICAO introduced strengthened language proficiency requirements for all pilots ATC controllers and aeronautical station operators who are now required to demonstrate a minimum English language proficiency at ICAO Level 4 Operational English language proficiency is a vital safety issue While Standard Phraseology is the most important factor of effective ...verbal communication it is recognized that there may be circumstances where plain language communications in English become necessary Difficulties in plain language communications between ATC and flight crews have often contributed to serious incidents and accidents In recognition of this ICAO has introduced the new focus on Plain English which is necessary inflight operations when Standard Phraseology is not enough This is particularly relevant in non routine or emergency situations