Aviation English is Distinct from Conversational English: Evidence from Prosodic Analyses and Listening Performanc

International aviation professionals converse in a register of English derived from postwar radiotelephony. Decades of use and regulatory pressure established Aviation English (AE) as the lingua franca for pilots and air traffic controllers. Recently, the International Civil Aviation Organization (ICAO) required aviation professionals prove AE proficiency, resulting in development of a variety of AE programs and tests derived from English language pedagogy, without accounting for unique aviation language requirements. This dissertation explores linguistic characteristics that must be accounted for in international AE programs.;Historically, issues of English language dominance were sidestepped by letting speakers of regional languages use their own aviation jargon, allowing native English speakers (NESs) to claim AE proficiency without learning a language comprehensible to international AE users. By allowing limited "plain language" use, this practice paved the way for colloquial jargon that is often opaque to non-native English speakers (NNESs). This led to an ICAO requirement that international pilots and controllers have conversational English (CE) proficiency.;A phonological examination of AE must begin by defining a baseline in comparison with other language forms. Regarding AE, it is critical to determine if there are differences with CE, because of the assumption of compatibility inherent in ICAO proficiency requirements. This dissertation compared AE with CE by examining the prosody and intelligibility of each language variety.;Prosodic differences in AE and CE were examined in two radio corpora: air traffic controllers and radio newscasters. From these data I examined rhythm, intonation and speech rate differences that could affect intelligibility across registers. Using laboratory studies of pilot and non-pilot NESs and NNESs, I examined AE intelligibility differences based on language background. NNES pilots scored worse on CE tasks and better on AE tasks than NES non-pilots, indicating CE proficiency is not a predictor of AE proficiency.;Dissertation findings suggest AE language training should focus on AE and not on CE, as is current practice. Given phonological and other differences between AE and CE, enlisting all AE users to learn and adhere to AE phraseology will save time and money in training and alleviate miscommunication and confusion in flight, potentially saving lives.