Information Overload in ATC

Information Overload in ATC

62ND ANNUAL CONFERENCE, Montego Bay, Jamaica, 8-12 May 2023

WP No. 158

Information Overload in ATC

Presented by PLC



Towards achieving their goals of providing a safe and efficient air traffic control service, many Air Navigation Service Providers (ANSPs) started improving their ATC systems by adding new tools to help ATCOs in their duties. The question is to what extent the development is improving performance and where should it stop?

This working paper aims to highlight the need for prudence regarding the continuous implementation of new software into existing ATC systems, to prevent ATCOs’ overloading.


1.1. Air traffic continues to increase worldwide.

1.2. At the same time, safety has increased constantly over the last 30 years.

1.3. However, air travel is only as safe as the airline operator, the air navigation service provider (ANSP), the equipment and the training procedures. Increasingly, ANSPs are implementing new systems and tools to achieve their goals of providing a safe and efficient air traffic control service. To facilitate this, they need to not only be safe and fit for purpose, but they have to integrate with existing systems to ensure they operate in a harmonized and efficient way.

1.4. Area, approach and tower control systems are constantly changing to help ATCOs better perform their duties. Some changes involve completely new systems, others just add new tools to existing systems.

1.5. This paper will examine some of the processes and considerations when introducing new ATC systems or new tools, continuing the analysis started in 2016 with the “Cognitive Processes in Air Traffic Control” paper presented by PLC.


Change Proposals

2.1. The progress of technology can lead to a change proposal. And this change could be an important one, with a big operational impact, like the change of paper flight strips to electronic flight strips, or could be a change with a smaller impact, like new labels or new windows added.

2.2. Is this statement completely true? Adding new labels, new information or new windows have a small impact on the system? At a closer look, the situation could be more complicated or even different.

2.3. New tools are being proposed to ATCOs constantly. They come along with new labels and even new windows. There are two different situations, but in the end, the result can be the same.

2.4. The first situation is when the new information displayed on the screen, or the new labels added reach a number where they are too many. In this situation, ATCOs could ignore them or, if the possibility exists, could hide or deactivate them. Hiding those pieces of information could lead to unwanted events. The impact can be even worse when it is deactivated a function like Minimum Term Conflict Detection (MTCD) / Short Term Conflict Alert (STCA). Thus, ignoring some information, hiding or deactivating it could be seen as a symptom of ATC having too much information to deal with.

  • In August 2022, an incident took place at the vertical border between two Romanian ACC sectors shortly after changing shifts (Annex 1). The Lower Sector transferred an aircraft to Middle Sector even though it had essential traffic at its flight level. From four ATCOs (two Executives and two Planners) only one had the MTCD window selected. None of them detected the conflict. The conflict was detected and announced by phone by Top Sector Planner. Immediately after, STCA was displayed. Both aircraft were instructed to turn right immediately. MTCD / STCA messages were exchanged between aircraft.
  • This is an example of an incident in which the conflict could have been detected earlier if the MTCD function had been activated. Unfortunately, this was not the case. Because there are too many settings to be made and too many windows to be checked, when assuming the duty, the possibility of not performing all of them exists.
  • ATCOs could be bothered or artificially tired.
  • This could be seen as a symptom of the ATC having too much information available to them. Then they are forced to decide what will and will not be displayed, possibly resulting in an incident as the one described.

2.5. The second situation is when the news consists of new windows or even separate screens added to the system. In these cases, the information needs to be put on different windows or even screens because is too large to be displayed on the current one which is already full, or the information is not so important to be displayed on the current one.

2.6. In many cases, there is more than one window for every new tool. This means ATCOs need to learn and then remember how to reach the tool in order to use it. So, the many they are, the more complicated the paths to reach them! The challenge is to provide easy ways to actually get the information the ATCO is looking for.

2.7. In other cases, new screens are added because the windows on the current screen are already too many or because the information added is too large or needed not very often.

2.8. When ATCO takes control of duty, first of all, he/she adjusts equipment: level of sound, font and dimension of the text, filters for altitude, filters for restrictions, filters for adjacent sectors, etc. Many of them are not even in the same window and the whole process takes time and attention.

2.9. Since these actions are performed during controlling aircraft, most of them could be done automatically. And this is the biggest concern: safety function being deactivated unintentionally or intentionally for a short period of time and forgotten deactivated.

2.10. As described in WP No. 303 at the 55TH IFATCA Annual Conference, the cognitive capacity of an ATCO can be affected by (Cognitive Processes in Air Traffic Control – WP No. 303 at the 55TH Annual Conference, Las Vegas, USA, 14-18 March 2016, Presented by PLC):

  • Visual and auditory interference.
  • Complex systems/procedures.
  • Increasing workload.
  • Ageing.
  • Switching between multiple modes.
  • Distractions.

2.11. According to the American Psychological Association, there are situations when a person can be overloaded. APA (American Psychological Association – Dictionary of Psychology) describes cognitive overload, information overload, stimulus overload, sensory overload, and communication overload:

  • cognitive overload – the situation in which the demands placed on a person by mental work (the cognitive load) are greater than the person’s mental abilities can cope with.
  • information overload – the state that occurs when the amount or intensity of information exceeds the individual’s processing capacity, leading to anxiety, poor decision making, and other undesirable consequences […].
  • stimulus overload – the condition in which the environment presents too many stimuli to be comfortably processed by an individual, resulting in stress and behaviour designed to restore equilibrium.
  • sensory overload – a state in which one’s senses are overwhelmed with stimuli, to the point that one is unable to process or respond to all of them.
  • communication overload – a condition in which more information is presented to a person or a computer system than can be processed or otherwise effectively utilized by the person or system.

2.12. Before discussing how to reduce cognitive overload, it is important to recognise the signs of it:

  • making mistakes – making silly mistakes may be a sign that someone is struggling to fully focus due to cognitive overload.
  • regularly forgetting important information – if regularly struggling to recall information, it may be a sign of trying to remember too much.
  • inability to focus on a task – it is important to give full attention to the task at hand, but when the memory is overloaded, the mind goes elsewhere which makes it difficult to focus.

2.13. When building user interfaces, it is best that designers consider a collection of best practices, known as the User Experience (UX) Laws. Among them, at least two should be taken into close consideration:

  • The average person can hold only 7 (plus or minus 2) items in their working memory (Miller’s Law) (Miller, 1956). The longer the message is, the less of it people will read.
  • Increasing the number of choices will increase the decision time logarithmically (Hick’s Law) (Hick, 1952). Too many and too complicated choices reduce the odds of the user actually making a choice. It is a simple idea that says that the more choices you present your users with, the longer it will take them to reach a decision. The direct implementation of Hick’s Law is a design principle known as KISS (Keep It Short and Simple), which states that simplicity is the key for a system to work in the best way.

2.14. There are a few questions asked more and more often:

  • To what extent the development is improving performance and where should it stop for not being helpful anymore?
  • Can it become a problem for ATCOs, creating confusion and turning into a negative impact if too invasive?
  • Should be set a maximum number of labels/pieces of information on the current screen?
  • Should be allowed to ATCOs to hide or deactivate the ones considered not helpful?
  • Should be allowed personal customization of the screen with no limitations?

2.15. Having in mind the APA’s definitions and the UX Laws, it appears that the answers to the above questions are not so easy to find.

2.16. The ones who can ultimately say what is helpful or not in performing their job are ATCOs. As IFATCA Policy AAS 1.13 already states, ATCO’s have to be involved in the new projects in early stages, since the beginning. Because if they are asked for opinion at the end or near the end of the project, it could prove too late.

Change Fatigue

2.17. Through necessity, the aviation industry has become adept at implementing and managing change, and ATCOs are no exception. Indeed, the International Civil Aviation Organisation has dedicated an entire annex to safety management, a large part of which is devoted to the management of change (Convention on International Civil Aviation, Annex 19 (2016) ‘Safety Management’, 2nd ed.).

2.18. The constant pressure on ANSPs to develop safer and more efficient work practices results in constant change for aviation professionals, including controllers. While most understand the need for change, retaining some stability enables controllers to maintain a better understanding of their roles resulting greater proficiency (Bernerth et al., 2011).

2.19. This working paper goes into some depth regarding the ability of ATCOs to manage individual changes, in particular, risks associated with presenting controllers with too much information. However, few studies have explored the cumulative effect of multiple changes on controllers’ ability to manage change.

2.20. Change fatigue refers to the state when excessive change has led workers to feel exhausted and unable to further adapt to change (Cox et al., 2022). Although it has been studied extensively in other fields, notably in the medical professions, it’s not a concept that has been widely studied in aviation.

2.21. Change fatigue is more commonly studied in relational to organisational change. Repetitive reorganisations can create employee resistance to further organisational change (de Vries & de Vries, 2023). It has also been suggested that change fatigue can lead to exhaustion, a feeling of being depleted or overextended beyond one’s capacity to handle workplace demands – the energy to perform basic job tasks is gone and employees are left feeling drained (Berneth et al., 2011).

2.22. There is no doubt that the cumulative effect of multiple organisational changes can affect aviation professionals. However, in safety critical industries such as aviation and medicine, change fatigue clearly takes on a more critical dimension. For example, for ATCOs it may have the effect of reducing proficiency due to ever changing rules, procedures and equipment resulting in stress, exhaustion and resistance to change.

2.23. There comes a time when employees, including ATCOs, can handle only so much disruption and periods of stability can help alleviate the effects of change fatigue (Berneth et al., 2011). When implementing any change, ANSPs should be mindful not only of the discrete change being managed, but the cumulative effect of multiple changes within a short period of time.

2.24. Regarding the development of ATC systems, IFATCA has three main policies: one related to how the development should be carried out, one related to the balance between automation and human factors, and one related to cognitive processes.


Modern ATM systems are more and more complex. Safety critical tasks such as Radar Data Processing or Flight Data Processing rely on complex software packages while the increasing volume of air traffic makes the ATM system more and more dependent
on such software. As a consequence, a software failure may lead to a catastrophic situation. Therefore, new ATM systems shall be carefully designed, tested, and validated before being considered ready for implementation.

IFATCA Policy is:

Operational controllers shall be involved in the design, development, and implementation of new ATM systems. Their role shall include:

  • Establishing user requirements.
  • Defining operational training requirements prior to implementation.
  • Participating in the risk assessment process.
  • Validating the system.
  • Providing feedback in the further development of the system.

The design, development and implementation team of a new ATM system/equipment/tool shall include, as a minimum:

  • System developers – typically software and hardware engineers;
  • Project managers;
  • End-users – i.e. the operational controllers, supervisors and ATSEPs (Air Traffic Safety Electronics Personnel);
  • Legal experts;
  • Human factors specialists;
  • Safety specialists.


WC 10.2.5 AUTOMATION / HUMAN FACTORS (TPM – Version July 2022)

IFATCA Policy is:

Automation shall improve and enhance the data exchange for controllers. Automated systems shall be fail-safe and provide accurate and incorruptible data. These systems shall be built with an integrity factor to review and crosscheck the information being received.

The human factors aspects of Automation shall be fully considered when developing automated systems.

Automation shall assist and support ATCOs in the execution of their duties.

The controller shall remain the key element of the ATC system.

Total workload should not be increased without proof that the combined automated/human systems can operate safely at the levels of workload predicted, and to be able to satisfactorily manage normal and abnormal occurrences. Automated tools or systems that support the control function shall enable the controller to retain complete control of the control task in such a way so as to enable the controller to support timely interventions when situations occur that are outside the normal compass of the system design, or when abnormal situations occur which require non-compliance or variation to normal procedures. Automation should be designed to enhance controller job satisfaction.

The legal aspects of a controller’s responsibilities shall be clearly identified when working with automated systems. A Controller shall not be held liable for incidents that may occur due to the use of inaccurate data if he is unable to check the integrity of the information received.

A Controller shall not be held liable for incidents in which a loss of separation occurs due to a resolution advisory issued by an automated system.

Guidelines and procedures shall be established in order to prevent incidents occurring from the use of false or misleading information provided to the controller.


WC 10.7.6 COGNITIVE PROCESSES IN ATC (TPM – Version July 2022)

For more than 35 years, IFATCA has been drawing attention to the human in the ATM system. With the ATCO not being a line worker, but the highly skilled centre of the system, this apprehension is fully justified. It is still common that the human factor is
overlooked, and specialists are called in too late when implementing new systems and when introducing challenging working methods.

With the ATC world being on the eve of new technological breakthroughs, it is more important than ever to realize that controllers have to be able to mentally keep up with this and deliver at least the same quality in safety and efficiency. 

IFATCA Policy is:

Capabilities and limitations of cognitive processes shall be considered when addressing Human Performance and Human  Factors. As can be observed, the first two policies cited above are well developed, since the last one, related to human beings, is yet in the early stages.



3.1. The most valuable resource of the aviation system is the human resource. This is the reason any system development should focus on human resources specifically and how the development would better help performing their job.

3.2. The key to dealing with ATC software implementation is ATCOs involving since the first steps of the project.

3.3. The number of items displayed on one label and the number of items/information displayed on the current screen should be set after a dedicated study.

3.4. Safety tools should not be deactivated.

3.5. When implementing changes, they should not just be considered in isolation. The cumulative effect of multiple changes, or change fatigue, should also be considered for every change.


4.1. It is recommended that the following be added to the IFATCA policy on Automation/Huan Factors and inserted into the TPM:

WC 10.2.5 AUTOMATION / HUMAN FACTORS (TPM – Version July 2022)

The number of items displayed on one label and the number of items/information displayed on the current screen should be set after a dedicated study.

Safety tools should not be deactivated.

4.2. It is recommended that the following be added to the IFATCA policy on Fatigue in Air Traffic Control and inserted into the TPM:


ANSPs should be mindful of the effects of change fatigue, including increased levels of exhaustion and stress, when implementing multiple changes within a short time frame.

Where appropriate, ‘stable periods’ should be used to mitigate these effects.


IFATCA Technical and Professional Manual – The permanent record of the Federation’s technical and professional policies – Version 65.0, July 2022 – DETERMINING OPERATIONS READINESS OF NEW ATM SYSTEMS (AAS 1.13).

IFATCA Technical and Professional Manual – The permanent record of the Federation’s technical and professional policies – Version 65.0, July 2022 – COGNITIVE PROCESSES IN ATC (WC 10.7.6).

American Psychological Association – Dictionary of Psychology.

Convention on International Civil Aviation, Annex 19 (2016) ‘Safety Management’, 2nd ed.

Bernerth, J.B. et al (2011), ‘Change Fatigue: Development and initial validation of a new measure’, Work & Stress, Vol. 25, No. 4, October – December 2011, pp 321 – 337 at 321.

Cox, C.G. et al (2022), ‘Mapping the nomological network of change fatigue: identifying predictors, mediators and consequences’, Journal of Organizational Change Management, Vol. 35, Issue 4/5, pp 718-733.

de Vries, M.S.E and de Vries M.S. (2023), ‘Repetitive reorganisations, uncertainty and change fatigue’, Public Money & Management, Vol. 23, No. 2, pp 126-135.

Bernerth, J.B. et al (2011), ‘Change Fatigue: Development and initial validation of a new measure’, Work & Stress, Vol. 25, No. 4, October – December 2011, pp 321 – 337 at 323.

Bernerth, J.B. et al (2011), ‘Change Fatigue: Development and initial validation of a new measure’, Work & Stress, Vol. 25, No. 4, October – December 2011, at 322.

“Cognitive Processes in Air Traffic Control” – WP No. 303 at the 55TH Annual Conference, Las Vegas, USA, 14-18 March 2016, Presented by PLC.

“Human Factors Integration in New ATM Systems” – WP No. 159 at the 54TH Annual Conference, Sofia, Bulgaria, 20-24 April 2015, Presented by PLC.

“Ageing Air Traffic Controllers: Consequences on Job performance” – WP No. 302 at the 55Th Annual Conference, Las Vegas, USA, 14-18 March 2016, Presented by PLC.

Last Update: September 21, 2023  

September 17, 2023   99   Jean-Francois Lepage    2023    

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