Initial situation: FIS at the limit
The flight information service is a central component of flight safety for many general aviation pilots. It provides traffic information, weather information, support in emergencies and acts as an important point of contact in uncontrolled airspace. Unlike air traffic control in controlled airspace, however, its use is voluntary, which leads to highly fluctuating workloads.
The situation has worsened considerably in recent years. The FIS sectors regularly reach their capacity limits, especially on good flying days during the season. Large geographical areas of responsibility - for example in the FIR Langen - meet a high number of aircraft being serviced at the same time. This often means that pilots are unable to establish radio contact or have to put up with waiting times.
DFS Deutsche Flugsicherung has therefore been looking for ways to utilise existing resources more efficiently without compromising safety.
Introduction of the Frequency Monitoring Code (FMC)
The Frequency Monitoring Code (FMC) was introduced for the first time in a selected sector during the 2025 flight season as part of a temporary trial operation. The aim of this procedure is to relieve the radio frequencies and at the same time improve the situation overview for the FIS controllers.
The basic principle is simple but effective:
Pilots receive a special transponder code (squawk) that signals that they are listening to a specific FIS frequency without being in active radio contact. The controller thus recognises that the aircraft can always be reached if this becomes necessary - for example, for traffic instructions or safety-relevant information.
This creates a kind of „passive participation“ in the FIS, which makes it possible to reduce radio traffic to the essentials.
Clarification: No „FIS-light“
It is important to make a clear distinction from possible misinterpretations: The FMC procedure is not a slimmed-down FIS service. Pilots who actively require information or want traffic information must continue to make regular radio contact.
The FMC should rather be seen as a supplement - a tool to relieve the frequencies and at the same time improve the accessibility of aircraft. The full FIS service is still available without restriction if it is actively utilised.
Positive experiences from the year 2025
The feedback from pilots and air traffic control on the first trial operation was overwhelmingly positive. The following were particularly emphasised:
- A noticeable relief of the radio frequencies
- Less „blocking“ due to unnecessary or redundant radio messages
- Improved accessibility in situations that are actually relevant
- More flexibility for pilots, who can decide when to actively participate in the radio depending on the situation
From an operational point of view, it was also shown that controllers can obtain a better picture of the situation if more aircraft can be identified via the FMC.
Extended trial operation from April 2026
Based on this experience, the process is now being rolled out further. From the AIRAC cycle in April 2026, specifically from 16 April 2026, an extended trial operation will start in other sectors.
The detailed framework conditions will be published in the corresponding Aeronautical Information Circular (AIC), which is due to be published on 2 April 2026. It will contain, among other things:
- The FIS sectors concerned
- Associated frequencies
- Assignment of FMC squawk codes
- Procedure description for pilots
This provides pilots with a binding basis for use in daily flight operations.
Classification in an international context
The FMC procedure is not an isolated German phenomenon. Similar approaches already exist in other European countries. In the UK, for example, so-called „listening squawks“ have been used for years with a similar aim: to reduce unnecessary radio communication while improving traffic information at the same time.
Experience from these countries shows that such procedures can make a noticeable contribution to reducing congestion, particularly in heavily frequented airspace.
Significance for general aviation
The FMC has several advantages for general aviation pilots:
- Increased probability of receiving relevant traffic information
- Reduction of radio congestion and waiting times
- More personal responsibility with improved integration into the overall system
- Better integration in complex airspaces with high traffic volumes
At the same time, the personal responsibility of pilots remains high. Listening to a frequency does not replace active airspace observation or the obligation to avoid collisions.
Outlook
By extending the trial operation from April 2026, DFS is taking a further step towards modern, flexible procedures in uncontrolled airspace. If the FMC procedure continues to prove its worth, permanent implementation is conceivable in the future.
In view of the continuing rise in traffic figures in general aviation and the increasing complexity of airspace, the need for such innovative solutions is likely to continue to grow. The Frequency Monitoring Code could establish itself as an important building block for more efficient and safer flight operations.
Source references:
AOPA
