Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled airspace. The primary purpose of ATC worldwide is to prevent collisions, organize and expedite the flow of air traffic and provide information and other support for pilots. In some countries, ATC plays a security or defensive role, or is operated by the military‖.

According to the paragraph, we can say that the air traffic controllers ____________________________.