It has been over a decade since the International Civil Aviation Organization proposed Language Proficiency Requirements to improve aviation English proficiency and air safety through adequate aviation English tests. Yet, many of the aviation English assessment procedures appear to not meet international professional standards for language tests. As a preliminary synthesis of the target language use (TLU) domain, this study aimed to derive authentic target tasks, task phases, and professionally relevant assessment criteria for an aviation English assessment in the context of Korean military aviation. Empirical evidence was gained through the values and views expressed by 81 air traffic controllers. Utilizing a task-based needs analysis, this study identified 40 target tasks with estimated difficulty level and perceived importance. The analysis of participant-generated target tasks revealed 14 target task phases in the TLU situations. A thematic analysis revealed indigenous assessment criteria including four main theme groups -- ATC knowledge, ATC skills, communication skills, and Controller characteristics. Current research findings could assist test developers in designing more authentic and specific aviation English assessment tasks by reducing constraints and reflecting the characteristics of TLU domains, offering useful means of observing successful or unsuccessful completion of the tasks to raters and test users.