Modeling ATM day to day operations A functional model of the ATM system Paula Luisa Santos, Paulo Monteiro Projects and engineering department NAV Portugal Lisbon, Portugal Email: paula.santos@nav.pt, paulo.monteiro@nav.pt Abstract— How can one say that current systems of Air Traffic Management (ATM) systems are safe and resilient? What is the current knowledge and understanding of these systems? Why is it necessary to know them better? The Model of ATM Reality In Action (MARIA) is a knowledge database and an automation framework developed by NAV Portugal to answer the above questions and to provide a sound base for safety analysis, namely by describing the whole system and the interdependencies between its functions. It is coded as a graph giving additional possibilities of automatic analysis. It has undergone extensive validation and is considered mature. Experimental work has been done on hazard and cause identification with success. MARIA is neither a business nor safety model. It is built to allow several perspectives of analysis depending on the aim at hand. It may be used in simulations to identify strong and weak points, to evaluate risk mitigation strategies and for other purposes. Modeling the dynamics and the unknown are areas of planned study using the emergent methods for the modeling of complex systems. Having a repository covering all that is done to provide an ATM service, in a systematic and uniform way, structured in a top- down manner, with the human as an integral part of the system, allowing automation of analysis and representation are significant advantages to improve understanding, safety and resilience of the ATM services. Sharing this knowledge database and adding the contributions from other models and interested partners will be beneficial for the ATM world. Keywords- System modeling; safety; resilience; complex systems; ATM functions; ATM information flows I. INTRODUCTION Have you ever wondered looking above your heads into the skies how safe should we feel down here? The busiest airports handle more than 100 flights per hour during peak hours, and there were on average more than 100 000 flights per day around the globe in 2014, this is what makes it to say that accidents and incidents are rare; that current systems of Air Traffic Management (ATM) are safe and resilient. But to what level are they known? What is the current knowledge and understanding of these systems? Why is it necessary to know them better? This paper argues that, in order to better understand a system or phenomena a model, i.e. a simplified version of reality, is a useful tool and as safety is a property of a system, not a property of the components that comprise the system [1], to analyze it, a global picture is required. This is the starting point for the work being presented. The ATM model presented in this paper, Model of ATM Reality In Action (MARIA), was developed by NAV Portugal to answer the above questions and to provide a sound base for safety analysis, namely by describing the whole system and the interdependencies between its functions. The following goals were defined at the start of this endeavor:  Give a global view of the system (people, procedures and equipment)  Show the dependencies between functions / processes  Build a description of the system architecture  Be the reference for future safety assessments  Come up with a systematic and reproducible hazard identification method  Help the definition of risk mitigation strategies Therefore, this paper will begin by giving some background on what falls under the field of ATM and the limitations of current approaches to ATM systems that led NAV Portugal to this modeling work. On a second chapter, the analysis methods, as well as the process to build MARIA are described, covering also the modeling decisions and the aspects that differentiate it from other existing models. The results of this work, its current status on a theoretical, as well as on experimental level, are presented next. The evolution presents ideas on possible future work. The conclusion will gather our main findings, and what those findings allow us to foresee as key next steps into more secure/resilient ATM systems and international cooperation. II. BACKGROUND For the purpose of this work an ATM system is defined as all that is required to expedite and maintain a safe and orderly flow of traffic during all flight phases and comprising the interaction between people, procedures and equipment.