The language of international aviation communication is English, but numerous aviation incidents and accidents have involved miscommunication between pilots and air traffic controllers, many of whom are not native speakers of the language. In 2004 the International Civil Aviation Organization (ICAO) published a set of Language Proficiency Requirements and a Proficiency Rating Scale, and by 5 March 2008, air traffic controllers and pilots were required by the ICAO to have a certificate attesting to their proficiency in the language used for international aeronautical communication. Although some organizations made efforts to produce tests by the deadline, in the event an implementation period was allowed, with a new deadline of March 2011. This article describes a number of surveys of tests of aviation English, the implementation of the ICAO requirements, and the rating scales. It concludes that many of the assessment procedures appear not to meet international professional standards for language tests, the implementation of the language assessment policy is inadequate, and much more careful and close monitoring is needed of the quality of the tests and assessment procedures required by the policy.