Air Traffic Service (ATS) is a broad term that encompasses several key functions. These include flight information services, alerting services, air traffic advisory services, and air traffic control services. According to the International Civil Aviation Organization (ICAO) Doc 4444 PANS-ATM, ATS plays a crucial role in ensuring safe air travel.
The main goals of ATS, as outlined in ICAO Annex 11, are to prevent collisions between aircraft and between aircraft and obstacles on the maneuvering area. It’s important to note that this does not cover the apron, and ATS does not aim to prevent collisions with terrain. Additionally, ATS seeks to facilitate an orderly flow of air traffic and provide valuable advice for the safe and efficient operation of flights. They also notify organizations about aircraft needing search and rescue assistance.
The air traffic control (ATC) service primarily aims to achieve the first three objectives. While these objectives apply universally across ATC units, the second one is specifically relevant to aerodrome control units. The flight information service (FIS) addresses the fourth goal, while the alerting service corresponds to the last objective. There is also an advisory service, which acts as a temporary measure to ease the transition from FIS to ATC, though it does not have specific objectives.
Air traffic services are delivered by designated air traffic service units (ATSUs). An ATSU can provide multiple services; for instance, an air traffic control unit might also offer flight information and alerting services. The type of service provided varies based on factors like the types of traffic—commercial air transport or general aviation—traffic density, available equipment, weather conditions, and geographical features such as mountains or open waters.
Once these factors are analyzed, airspace classification is established, leading to the formation of appropriate ATSUs. The level of service is determined by the airspace class and the specific ATS unit. An ATC unit typically offers ATC service, FIS, and alerting service, with FIS often taking a lower priority. Conversely, an FIS unit will not provide ATC services. If an ATC unit oversees uncontrolled airspace (class G), it will only deliver FIS and alerting services in that region, even though it is an ATC unit.
