Continuous growth of aviation industry necessitates developing a better understanding of English for Specific Purposes teaching settings to improve the quality teaching and in turn, to serve best for the needs of ESP students. Therefore, role of ESP teachers and their experiences in these teaching settings need to be closely monitored for improved professional development opportunities. Taking this into account the present study focused on ESP teachers working and giving Aviation English courses in a tertiary level institution in Turkey. The constructivist approach was adopted to uncover the challenges encountered by ESP teachers in the target setting. Five ESP teachers were observed for a 45-minute period by the researcher to become familiar with their in-class practices. Then, semi-structured interviews were conducted with participants by asking them to reflect on their in-class practices to develop a better understanding of their instructional challenges. The findings of this qualitative study revealed that (1) low self-efficacy and low contextual knowledge were the most prominent challenges of ESP teachers and that (2) lack of professional development programs and inexperience in ESP teaching were the underlying reasons for those challenges. In this sense, the present study offered important insights into ESP teachers’ long-neglected yet crucial instructional challenges.