Air travel in the U.S. grew at a rapid pace until 2001, expanding from 172 million passenger enplanements in 1970 to nearly 615 million in 2000.

However, over the next 3 years, a combination of factors—the events of September 11th, 2001, an economic recession, and other factors—combined to reduce traffic back to 1995 levels. Nevertheless, air travel remains one of the most popular modes of transportation.

Airlines in this industry transport passengers and freight over regularly scheduled routes or on routes, called “charters,” specifically designed for a group of travelers or a particular cargo. Several classes of airlines function in the United States.