Which act allowed airlines to freely enter or leave markets and set fares independently?

The Airline Deregulation Act is significant because it transformed the airline industry by allowing airlines to enter or exit markets without government restrictions. This law, passed in 1978, marked a shift from a regulated environment where the government controlled routes, schedules, and fares to one where market forces dictate these factors. As a result, airlines gained the freedom to set their own fares based on competition and demand, which fostered a more dynamic and competitive aviation market. The choices related to the Commercial Aviation Reform Act, Transportation Security Act, and Federal Aviation Act pertain to different aspects of aviation regulation or security, but they do not specifically address the deregulation of airline fares and market entry like the Airline Deregulation Act does.