The dynamic, integrated management of air traffic and airspace including air traffic services, airspace management and air traffic flow management — safely, economically and efficiently — through the provision of facilities and seamless services in collaboration with all parties and involving airborne and ground-based functions.
Source: ICAO Doc 4444 PANS-ATM
The aggregation of the airborne and ground-based functions (air traffic services, airspace management and air traffic flow management) required to ensure the safe and efficient movement of aircraft during all phases of operations.
Air traffic management comprises three main services:
Air traffic services (ATS), with the general purposes of ensuring safe and orderly traffic flow (facilitated by the air traffic control (ATC) service) as well as providing the necessary information to flight crews (flight information service, FIS) and, in case of an emergency, to the approprate (e.g. SAR) bodies (alerting service). ATS is mostly performed by air traffic controllers. Their main functions are to prevent colisions by e.g. applying appropriate separation standards and issue timely clearances and instructions that create orderly flow of air traffic (e.g. accomodate crew requests for desired levels and flight paths, ensure continuous climb and descent operations, reduce holding times in the air and on the ground). ATS relies on tactical interventions by the controllers and direct communication with the flight crews usually during the entire flight.
Air traffic flow management (ATFM), the primary objective of which is to regulate the flow of aircraft as efficiently as possible in order to avoid the congestion of certain control sectors. The ways and means used are increasingly directed towards ensuring the best possible match between supply and demand by staggering the demand over time and space and also by ensuring better planning of the control capacities to be deployed to meet the demand. Supply and demand can be managed by imposing various restrictions on certain traffic flows (e.g. assigning CTOTs or requiring flights matching certain criteria to use specific routes). Also, supply can be increased by appropriate setcor management (e.g. increasing the number of controllers working at the same time). AFTM measures can be seen as pre-tactical, as they do not affect the current situation but rather the near future.
Airspace management (ASM), the purpose of which is to manage airspace - a scarce resource - as efficiently as possible in order to satisfy its many users, both civil and military. This service concerns both the way airspace is allocated to its various users (by means of routes, zones, flight levels, etc.) and the way in which it is structured in order to provide air traffic services.
The diagram below shows the structure of ATM and explains the relations between ATM, ATS and ATC.