A legacy carrier, in the United States, is an airline that had established interstate routes by the time of the route liberalization which was permitted by the Airline Deregulation Act of 1978 and was thus directly affected by that act. It is distinct from a low-cost carrier (a term fostered as a form of disparagement against post-deregulation start-up air carriers, and the traditional airlines' once heavily unionized work groups), which in the United States are generally new airlines that were started to compete in the newly deregulated industry.