Airport control towers house the workers and much of the technology underpinning modern aviation. In the U.S., the Federal Aviation Administration owns, builds and operates most control towers and provides air-traffic-control services at 264 airports.

In contrast, air-traffic control in some countries is privatized. For example, Nav Canada, a private non-profit corporation, has been responsible for air traffic control since 1996 in Canada, and other countries in which private air-navigation-service companies operate include Germany, Italy, Switzerland, Norway, Poland, the Ukraine and Indonesia.