Airline services were historically heavily regulated, in part because of concerns about monopoly and oligopoly arising from the fact that, in most cases, only a small number of airlines serve a given "city pair" market by providing direct flights between the cities concerned.
Airline deregulation began in the US in 1978 with the Airline Deregulation Act. Many other countries have subsequently deregulated their domestic markets, and a similar process has applied to airline markets within the European Union. However, many international airline markets remain subject to tight regulation.
 Airline deregulation in the United States
Prior to 1978, the Civil Aeronautics Board (CAB) controlled many aspects of domestic aviation in the United States. In particular, airlines required permission to serve any given route and incumbents could raise many obstacles to the granting of permission. The system was dismantled as a result of the Airline Deregulation Act.
(main article Airline Deregulation Act) this is how it takes place
 Airline deregulation in Australia
Prior to 1990, Australia operated a Two Airlines policy' which effectively guaranteed the maintenance of exactly two airlines, one public (TAA, later Australian Airlines and then Qantas) and one private (Ansett), with almost identical fares, fleets and schedules. Discounting was only permitted to the extent that it did not necessitate an increase in standard economy fares. With the repeal of the two airlines agreement under the Airline Agreement Termination Act, which came into effect on 30 October 1990,...