Changes in the air ambulance industry’s size and structure have led to differences of opinion about the implications for air ambulance use, safety, and services. Some industry stakeholders believe that greater state regulation would be good for consumers. While states can regulate the medical aspects of air ambulances, the Airline Deregulation Act (ADA) preempts states from economic regulation—i.e., regulating rates, routes, and services—of air ambulances. Other stakeholders view the industry changes as having been beneficial to consumers and see no need for a regulatory change. Asked to review the U.S. air ambulance industry, GAO examined (1) changes in the industry in the last decade and the implications of these changes on the availability of air ambulances and patient services and (2) the relationship between federal and state oversight and regulation of the industry. GAO analyzed available data about the industry; synthesized empirically based literature on the industry; visited four air ambulance providers with differing views on the industry changes; and interviewed federal and industry officials. Read “Air Ambulance: Effects of Industry Changes on Services Are Unclear”,GAO-10-907, September 30 at http://www.gao.gov/products/GAO-10-907.