Separation minima infringements
What this relates to:
To facilitate the safe navigation of aircraft in controlled airspace, authorities specify vertical and horizontal distances, known as separation standards. The standards ensure that aircraft are separated in a safe manner. If this minimum distance between two aircraft is not achieved, aviation terminology refers to as a separation minima infringement (SMI). This can happen if a pilot fails to follow air traffic control instructions or if air traffic control itself is unable to ensure the minimum separation.
Example:
Two aircraft start one after the other from the same airport on the same route. The private jet is faster than the commercial aircraft in front of it and catches up to it. For a brief moment, they undershoot the separation standards. The air traffic controller instructs the private jet to correct its flight path, thereby ensuring that the separation of the two aircraft is safe again in accordance with the standard.
Remarks on the 2024 figures:
In 2024, the FOCA again registered an increase in the number of separation minima infringements (SMI) in Swiss airspace and the airspace delegated to and managed by Skyguide. An in-depth analysis has shown that this increase can be explained by the growing number of reports from LSZH TWR/APP and is partly due to a new reporting category known as wake turbulence separation minima infringements.
Example: A small aircraft is approaching the airport directly behind an Airbus A380. Larger aircraft create air turbulence that can affect smaller aircraft. To ensure that the smaller aircraft is not endangered, a certain minimum distance must be maintained. If this minimum distance cannot be maintained, it is referred to as a wake turbulence separation minima infringement.
However, the number of separation minima infringements also increased without this additional category. Compared to the previous year, reports in 2024 (per 10,000 aircraft flight movements) increased by 25%. On the other hand, the average severity level decreased again and is roughly back to the 2018–2022 average. This suggests that the increase in the average severity level in 2023 was an exception, but it will continue to be monitored.
