The Erlanger Health System (often referred to as Erlanger Hospital or simply Erlanger), incorporated as the Chattanooga-Hamilton County Hospital Authority, a non-profit, public benefit corporation registered in the State of Tennessee, is an academic system of hospitals, physicians, and medical services based in Chattanooga, Tennessee. Erlanger is a tertiary referral hospital and Level I Trauma Center serving a 50,000 sq mi (130,000 km2) (125 mi (201 km) radius) region of East Tennessee, North Georgia, North Alabama, and western North Carolina. The system's critical care services are accessible to patients within a 100 mi (160 km) radius through five Life Force air ambulance helicopters, each equipped to perform in-flight surgical procedures and transfusions.