Pilots must undergo a rigorous physical examination to obtain a Medical Certificate, which varies in depth based on the "Class" required (First, Second, or Third). A First-Class Medical, required for airline transport pilots, involves a comprehensive review of the cardiovascular system, including an electrocardiogram (ECG) to detect heart abnormalities. The examiner tests visual acuity (must be 20/20 corrected), color vision, and hearing through audiometry. They also check for neurological health, mental health stability, and equilibrium. Laboratory tests typically include a urinalysis to screen for glucose (diabetes) or protein (kidney issues) and a drug screen. For pilots over 40, these evaluations occur every six months to ensure they remain fit for the immense responsibility of flight safety.