Ground-based safety nets

We support the prevention of imminent or actual hazardous situations from developing into major incidents or even accidents.


Safety nets help prevent imminent or actual hazardous situations from developing into major incidents or even accidents. Safety nets, for airborne phases of flight and for preventing collisions between aircraft or with terrain or obstacles, are either ground-based or airborne.

Ground-based safety nets are an integral part of the air traffic management (ATM) system. Using primarily air traffic service (ATS) surveillance data, they provide warning times of up to two minutes. Upon receiving an alert, air traffic controllers are expected to immediately assess the situation and take appropriate action.


To assist air navigation service providers (ANSPs) with the implementation of ground-based safety nets, we at EUROCONTROL have produced technical guidance material on ground-based safety nets for the best part of two decades. The latest edition of the Safety Nets Guidelines, known as ‘Level 3’ documentation, was released in 2017. It covers the following safety nets:

  • Short Term Conflict Alert (STCA)
  • Area Proximity Warning (APW)
  • Minimum Safe Altitude Warning (MSAW)
  • Approach Path Monitor (APM).

This work aims to maintain and, where possible, increase the effectiveness of ground-based safety nets in the context of increasing traffic density and evolving operational concepts.

Safety nets guide

Our guide gives useful information on using safety nets for maximum benefit, including a quick introduction to the subject, action areas for efficient implementation, life cycle est practices and more.

Safety Nets Guide

NetAlert newsletter

NetAlertis a news update for people working for air traffic control centres, airlines, and the organisations that support them.

NetAlert aims to increase awareness of how safety nets work, how they interact, and what is being done to help with implementing and enhancing them.