ComplexWorld Position Paper

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It is commonly agreed, and clearly reflected into the Lisbon Agenda and other EU declarations and treaties, that knowledge development and innovation shall be two of the cornerstones of the European economy. A strong collaboration between business, research centers, universities, and the public sector is acknowledged as a key requirement for a successful research and innovation strategy. These principles are also true for ATM: to remain competitive in the global market, long-term research and innovation are as vital for the European ATM industry as they are for any other industry.

Taking into account that ATM innovation cycles are typically between 15 and 20 years, the ATM community must look for "quick wins" that take advantage of already existing concepts and technologies, but also keep an eye on long-term, high-risk, potentially disruptive research that may bring the concepts and technologies that will be implemented 20 years from now.

All European-funded ATM research and development is now consolidated into SESAR. Whilst most of the SESAR programme is devoted to developing and putting in place the concepts outlined in the SESAR Concept of Operations, in most cases making use of technologies that are already (or almost) ready for implementation, the SESAR programme also includes a workpackage specifically devoted to long-term and innovative research: Workpackage E (WP-E).

The key contribution from Workpackage E will be twofold:

  • Firstly, it will be a catalyst to create a healthy European research capability for and related CNS (Communication Navigation Surveillance) that will persist beyond the lifetime of the current SESAR development programme. To achieve this goal, WP-E will have to stimulate creativity and innovation, develop new scientific and technical challenges beyond those currently identified, facilitate the sustainable development of ATM research capabilities, and promote ATM and air transport as a serious and challenging topic for study, encouraging graduates to seek careers in the discipline.
  • Secondly, it will provide funding for research activities that are not currently planned within the 'mainstream' SESAR development workpackages. Such research will address applications to become operational beyond the current SESAR timeframe (nominally 2020), as well as innovation that may have application in the nearer term and provide 'quick wins' for SESAR.

WP-E makes use of two main instruments:

  • Research Networks provide a structured way to build research knowledge, competence and capability, through a stable forum allowing the development, exchange and dissemination of knowledge among multidisciplinary groups of organisations (academia, industry, research establishments...) that share a common interest in a relevant domain.
  • will explore new ideas falling outside the other SJU workpackages. These will be mainly long-term, high-risk and/or high-potential research ideas, but there may be also room for innovative projects with application in the shorter term.

The number of WP-E research themes is initially limited to four. These research themes were defined following broad consultation with experts from academia, industries and various research organisations, the SESAR Scientific Committee and the European Commission. WP-E networks and projects are expected to address the following research themes:

  • Legal Aspects of Paradigm Shift;
  • Towards Higher Levels of Automation in ATM;
  • Mastering Complex Systems Safely; and
  • Economics and Performance.

ComplexWorld is the Research Network for the theme 'Mastering Complex Systems Safely'.


Complex Systems Science is one of a number of names given to the study of Complex Systems, also known as Complexity Theory, Complex Systems Theory or Complexity Science. This kind of system can be defined as the collection of a high number of parts (elements, individuals, agents...) that interact with and adapt to each other, such that the system exhibits behaviours at the system-wide level that emerge from the combined actions of individuals (emergent behaviour) and cannot be understood only from the information stored at the individual level. Understanding how these interactions create the collective emerging behavior is not a trivial task, as emergence carries with it the additional implication that these phenomena typically cannot be predicted by examining the individuals' behaviour alone.

Complexity Science is not a single theory, but it is highly interdisciplinary and encompasses a set of ideas, methodologies and tools from different fields, such as nonlinear dynamics, statistical physics, artificial intelligence, or numerical simulation, among others.

The ATM system exhibits some characteristics that make it suitable for analysis from a Complexity Science approach. Let us enumerate the most relevant:

  • large number of components;
  • heterogeneous components: airports, regulations, flights, natural conditions, etc.;
  • multiple temporal and spatial scales;
  • highly structured system: there is an airport network structure, on the one side, and many different layers (commercial, regulation, passengers, traffic) on the other;
  • complex structure of the interactions between pairs or groups of different components;
  • adaptive to the changing external environment;
  • system of systems, i.e. single components as airports may also exhibit complex features;
  • self-organization;
  • non-determinism.

All these characteristics together give rise to emergent behaviours, a fingerprint of complex systems. However, most effort made so far in air traffic modelling has not taken into account this paradigm. The WP-E research theme 'Mastering Complex Systems Safely' will explore how Complexity Science can contribute to understand, model, and ultimately drive and optimise the behaviour and the evolution of the ATM system that emerges from the complex relationships between its different elements.

The ComplexWorld Network is an open partnership between universities, research centers, and industry, aiming at:

  • fostering the interaction and cross-fertilization between the Air Transport and the Complex Systems research communities,
  • identifying the state-of-the-art in the relevant disciplines,
  • defining and describing the main research challenges and their potential benefits for the ATM system, in order to set direction for future research and create a momentum of research in the field,
  • attracting talented Complex Systems researchers towards ATM; and
  • defining, developing and maintaining a clear roadmap for establishing and consolidating a research community at the intersection of Complexity and ATM of clear added value for the European ATM sector.

CW position paper

The Complex ATM Position Paper is the common research vehicle that defines the high-level, strategic scientific vision for the ComplexWorld Network. The purpose of this document is to provide an orderly and consistent scientific framework for the WP-E complexity theme.

The specific objectives of the position paper are to:

  • analyse the state of the art within the different research areas relevant to the network, identifying the major accomplishments and providing a comprehensive set of references, including the main publications and research projects;
  • include a complete list of , a list of application topics, and an analysis of which techniques are best suited to each one of those applications;
  • identify and perform an in-depth analysis of the most promising research avenues and the major research challenges lying at the junction of ATM and complex systems domains, with particular attention to their impact and potential benefits for the ATM community;
  • identify areas of common interest and synergies with other SESAR activities, with special attention to the research topics covered by other WP-E networks.

An additional goal for future versions of this position paper is to develop an indicative roadmap on how these research challenges should be accomplished, providing a guide on how to leverage on different aspects of the complexity research in Air Transport.

Research Themes

The authors of this document conceive the position paper as a reference document, not just as a review paper (although it does review the state of the art). That is, the paper not only reviews what has been done until now, but also it must provide guidance for future research in the subject matter. Moreover, it is not a research paper, although it may include research results needed to illustrate the guidelines it provides.

The main part of the document is composed of five articles which analyse the following research themes:

  1. Uncertainty;
  2. Emergent behaviour;
  3. Complex data analysis;
  4. Non-classical, complex performance metrics;
  5. Resilience.

These sections are self-contained, including their own reference lists. For each section, after an introductory part, in which the general objectives, the main definitions and the scope of the research theme are stated, several research lines and case studies are identified.

The research lines are the main topics for analysis. For each one of them, the problem to be addressed is stated, a literature review is made, and some research challenges (intrinsic to the research line and not linked to any specific application) are identified. Being encyclopaedic is not a goal of this document; on the contrary, the research lines identified are only those considered most relevant for the research theme under study. The list of research lines is not closed, and can change as the position paper evolves.

The case studies present certain issues which, once they are overcome, could improve the performance of the ATM system. These issues can be tackled through one or several research lines. Whereas the research challenges (corresponding to each research line) are focused on fundamental research, the case studies are focused on innovation.

The structure of the position paper is shown schematically in the next figure.

It must be noted that this document has been produced by different authors with diverse backgrounds (physicists, engineers, technical managers) and, therefore, with different understandings of what research lines, research challenges and case studies are. Hence, a certain level of heterogeneity has been unavoidable.

Another point that must be noted is that, once the five sections have been produced, a number of transversal topics have emerged, that is, topics addressed by some (if not all) sections; they are the following:

  1. System scales: different scales are identified and analysed for the ATM system, corresponding to the different problems posed by the research themes.
  2. Network theory: the clear network structure of the air transportation system makes it convenient (and even necessary) to adopt the framework, tools and techniques of network theory.
  3. Growth and preferential attachment.



This project has received funding from the SESAR Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 783287.