The USA domestic air transport is deregulated for 25 years, since 1978. Airlines can operate any routes with any schedules, as well as any fares and levels of services since then, provided the FAA safety procedures are all met.
Such fierce competition makes the USA domestic flights with lowest fare per passenger km, thus making much more people switch to air travel because of much lower fare.
But such fierce competition also makes many airlines suffer heavy loss and hence closure of many airlines. What worse is the serious congestion of airports and airspaces, especially the northeast USA.
What do you think of USA domestic air transport deregulation since 1978?