In 2003, the International Civil Aviation Organization (ICAO) published its Language Proficiency Requirements (LPRs), requiring pilots and air traffic controllers (ATCOs) to demonstrate their ability to speak and understand the language used in radiotelephony communications. Over the years, multiple interpretations of the policy have led to practices that may have undermined the meaningfulness of the LPRs (ICAO, 2022). This is likely due to issues such as the presence of ambiguity and uncertainty in the policy as well as the lack of clarity regarding the nature of the language that needs to be assessed (e.g., Alderson, 2010;. Since the ICAO Test Design Guidelines (TDGs) recommend that tests should contain tasks dedicated to the assessment of listening separately from speaking, the goal of this doctoral research was to address the initial stages of the development of a test to assess pilots' listening comprehension in isolation: the definition of the listening construct. Construct definition is an essential step in test development and validation, and it forms the basis for the development of test specifications. To investigate what should be assessed in such a test, three perspectives were taken into consideration. A review of the academic literature and research was made to better understand the construct of listening tests, and, more specifically, the features of aeronautical English listening that may contribute to misunderstandings between pilots and ATCOs. An analysis of the ICAO rating scale was also conducted to examine the listening construct underpinned by the descriptors. Additionally, the perceptions of pilots and other key stakeholders regarding the assessment needs in relation to the listening performed by pilots in radiotelephony communications with ATCOs was investigated. The conceptual foundation underpinning this research project is the sociocognitive theory developed by Weir (2005), which takes into account both individuals' cognitive processes and the features of the context in which 1