Air Traffic Controllers direct aircraft safely through their assigned flight paths, involving a specific sector of airspace. Each sector is controlled by at least one Air Traffic Controller often through the use of radar, which gives a greater volume of traffic to the sector.
An Aerodome controller, also known as a Tower Controller, is responsible for controlling aircraft within the direct airspace of an airport. These controllers use visual observation from the tower as well as sometimes utilizing radar approach control positioning where needed at high volume facilities.
Aerodome Controllers work in a group of positions including Flight Data, Ground, Local, and Approach. Each position holds its own specific role in the safe arrival and departure of aircraft.
Flight Data/Clearance controllers will issue flight plan clearances before aircraft taxi the runway. Unlike the other positions, Data/Clearance will only involve departing aircraft, thus limiting their traffic to just half of the overall traffic of the sector.
Ground Control is responsible for issuing safe taxi instructions to the aircraft for movement on ramps as well as other non-movement areas of the ground. As the name states, this position deals with aircraft on the ground, either arriving or leaving the sector.
Local, also known as Tower Control, will issue instructions for the safe and orderly takeoff and landing of the aircraft in the sector. These controllers also issue authorization to aircraft for movements on or across the runways, preventing accidents through radar and visual control.
Approach Controllers are responsible for issuing the instructions to aircraft in the sector who are preparing to land. This involves directing them in a safe and consistent manner, as well as stacking them at various holding designations if necessary. All this must be done in a timely manner due to schedules and traffic needs.
In the military, an Air Traffic Controller will most likely be an enlisted person chosen and trained for the position, although exact terms will vary from country to country. In some countries the military is responsible for all of the air traffic control, whereas some countries have both military and civilian airspace controllers. Looking back through history, the role of an Air Traffic Controller was traditionally a government position. However, over the years several countries have moved on to privatize the system, making Air Traffic Control a public position.