Since miscommunication and language barriers are type of human error that could endanger individuals on board and threaten flight safety The International Civil Aviation Organization ICAO established English languange proficiency requirements for pilots and air traffic controllers who serve and operate on international flights Since miscommunication and language barriers are type of human error that could endanger individuals on board and threaten flight safety. The International Civil Aviation Organization (ICAO) established English languange proficiency requirements for pilots and air traffic controllers who serve and operate on international flights.