Background: Aviation professionals experience chronic stress due to prolonged work hours, irregular schedules, and exposure to altitude-related physiological challenges, leading to dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis. Controlled hypoxia has been proposed as a potential strategy for modulating stress responses and enhancing recovery. Objective: This study aimed to investigate the effects of a weekend of controlled normobaric hypoxia on key hormonal markers, including cortisol, prolactin, testosterone, and DHEA-S, in pilots and flight attendants. Methods: A within-subject experimental design was used with 10 participants (6 pilots, 4 flight attendants) exposed to two 12-hour sessions of normobaric hypoxia (simulated altitude: 3,500–4,000 m) during their designated rest period. Blood samples were collected at three-time points: baseline, pre-hypoxia, and post-hy...