The purpose of this paper is to reveal and discuss evidence that the safety and efficiency of international aviation continues to be adversely impacted by poor English language proficiency over the radio. In 2011, all members of the International Civil Aviation Organisation (ICAO) were declared to be compliant with regards to the English language testing of all pilots and air traffic controllers (ATCOs). However, language experts have continued to raise concerns about the regulatory framework of Language Proficiency Requirements (LPRs) and about whether an international standard of English language proficiency has truly been established. This paper describes the analysis of responses given by pilots and ATCOs to a survey which addressed the nature and frequency of poor language proficiency that they experience during flights. The data show evidence that there continues to be a problem of language proficiency among pilots and ATCOs, that this problem is encountered relatively frequently and that some regions of the world are experiencing it more acutely than others.