History of non-scheduled airlines in the United States
The history of non-scheduled airlines in the United States records the rise and fall of a uniquely unencumbered sector of the heavily regulated American airline industry from the end of World War II to the Airline Deregulation Act of 1978. Frequently operating in the shadow of colossal national airlines, which received federal subsidies and flew scheduled passenger service at costly rates, non-scheduled airlines were generally small companies which could be chartered to transport goods or passengers at an hourly or distance-based charge.
Source: Wikipedia — History of non-scheduled airlines in the United States (CC BY-SA 4.0)