The presented research evaluates the concept of providing an airport’s Air Traffic Control with a... more The presented research evaluates the concept of providing an airport’s Air Traffic Control with a bird strike advisory system. Such a system informs the controller about current and predicted bird movements in the arrival and departure corridors. Based on this information, the controller can decide to delay or reroute air traffic in order to prevent collisions with birds. To evaluate the resulting effects on the airport’s safety and capacity, fast-time simulations merging air traffic and bird movements, will be performed. To represent realistic bird movements, inputs from two different radar types are combined. For the close airport environment, historic bird tracks from avian radar installed at the considered airport serve as source. To cover the arrival and departure corridors up to 3000ft, the altitude up to which the largest majority of bird strikes occur, data from weather radar is used: based on bird densities and speed directions, bird tracks are generated for different altitude bands. The obtained tracks from avian and weather radar are combined in order to retrieve the overall image of bird movements in the close and extended airport area. This paper describes the methods for extracting, generating and finally combining the inputs from the two radar sources, in order to generate realistic bird movements. These will serve as a key input parameter for evaluating the effects of a bird strike advisory system with fast-time simulations.
Current investigations into urban aerial mobility, as well as the continuing growth of global air... more Current investigations into urban aerial mobility, as well as the continuing growth of global air transportation, have renewed interest in Conflict Detection and Resolution (CD&R) methods. With the new applications of drones, and the implications of a profoundly different urban airspace, new demands are placed on such algorithms, further spurring new research. This paper presents a review of current CR methods for both manned and unmanned aviation. It presents a taxonomy that categorises algorithms in terms of their approach to avoidance planning, surveillance, control, trajectory propagation, predictability assumption, resolution manoeuvre, multi-actor conflict resolution, considered obstacle types, optimization, and method category. More than a hundred CR methods were considered, showing how most work on a tactical, distributed framework. To enable a reliable comparison between methods, this paper argues that an open and ideally common simulation platform, common test scenarios, and common metrics are required. This paper presents an overview of four CR algorithms, each representing a commonly used CR algorithm category. Both manned and unmanned scenarios were tested, through fast-time simulations on an open-source airspace simulation platform.
How should traffic be structured to handle high density PAV/UAV traffic over urban areas? Four di... more How should traffic be structured to handle high density PAV/UAV traffic over urban areas? Four different Airspace designs are developed and evaluated concerning capacity, robustness, efficiency and safety.
The interest in urban air mobility as a potential solution for urban congestion is steadily growi... more The interest in urban air mobility as a potential solution for urban congestion is steadily growing. Air operations in urban areas can present added complexity as compared with traditional air traffic management. As a result, it is necessary to test and develop novel airspace designs and rules. As airspace in urban areas is a scarce resource, creating structures and rules that effectively utilise the airspace is an important challenge. This work specifically focuses on layered airspace design in urban operations constrained to fly between the existing buildings. Two design parameters of airspace design are investigated with two sub-experiments. Sub-experiment 1 investigates layer function assignment by comparing concepts from previous research with different layer assignment distributions. Sub-experiment 2 investigates the flight rules of vertical distribution of traffic within the airspace, to determine whether this is best achieved in a static (pre-allocated) or dynamic manner. Bo...
This paper presents an analysis of the potential fuel and emission benefits of implementing Conti... more This paper presents an analysis of the potential fuel and emission benefits of implementing Continuous Descent Operations at Schiphol International Airport, from cruise altitude to the final approach fix, for a large scope of aircraft types. Using historical data from on-board sources and ADS-B, fuel-optimal continuous descents are simulated using the total-energy model. By comparing the fuel consumption between historical flights and the simulated continuous descent flights, fuel benefits are found. CO2 emissions are then calculated linearly from the fuel benefits. The results show average savings of 92kg up to 500 kg of fuel per flight. For Schiphol, this results in a total of 39 million kg of fuel savings per, year leading to more than 123 thousand tonnes of CO2 savings per year.
This paper focuses on estimating aircraft mass and thrust setting using a recursive Bayesian meth... more This paper focuses on estimating aircraft mass and thrust setting using a recursive Bayesian method called particle filtering. The method is based on a nonlinear state-space system derived from aircraft point-mass performance models. Using solely ADS-B and Mode-S data, flight states such as position, velocity, and wind speed are collected and used for the estimation. An important aspect of particle filtering is noise modeling. Four noise models are proposed in this paper based on the native ADS-B Navigation Accuracy Category (NAC) parameters. Simulations, experiments, and validation, based on a number of flights are carried out to test the theory. As a result, convergence of the estimation can usually be obtained within 30 seconds for any climbing flight. The method proposed in this paper not only provides final estimates, but also defines the limits of noise above which estimation of mass and thrust becomes impossible. When validated with a dataset consisting of the measured true m...
How should traffic be structured to handle high density PAV/UAV traffic over urban areas? Four di... more How should traffic be structured to handle high density PAV/UAV traffic over urban areas? Four different Airspace designs are developed and evaluated concerning capacity, robustness, efficiency and safety.
The world population is expected to grow further with a major increase in population living in ur... more The world population is expected to grow further with a major increase in population living in urban areas. Exploiting the door-to-door concept to the full extent, a considerable part of conventional vehicles may be replaced by personal aerial vehicles. Cargo delivery system will the follow same philosophy using unmanned aerial vehicles. This brings up completely new challenges for future air traffic management in urban environments. The Metropolis research project investigates radically new airspace design concepts for the urban environments 50+ years into the future, which are extreme when compared to today in terms of traffic density, complexity and constraints. This work presents the results of simulation data analysis and a comparison of concepts of urban airspace design regarding organizational (complexity) metrics. The aim was to identify how the structure involved in the concept of urban airspace design influences the complexity of the traffic situation. In this work geometr...
This paper presents a semi-empirical method to determine the maximum theoretical capacity of dece... more This paper presents a semi-empirical method to determine the maximum theoretical capacity of decentralized airspace concepts. The method considered here, named Capacity Assessment Method for Decentralized ATC (CAMDA), formalizes an earlier approach described in literature, extends it for threedimensional airspace, and also improves the accuracy of the underlying models. CAMDA defines capacity as the traffic density at which conflict chain reactions propagate uncontrollably throughout the entire airspace. CAMDA identifies this critical density using a semi-empirical approach whereby models describing the actions of decentralized conflict detection and resolution algorithms are combined with empirically obtained conflict count data. The CAMDA method is demonstrated in this work for a decentralized direct routing en-route airspace concept that utilizes a state-based conflict detection algorithm, and a voltage potentialbased conflict resolution algorithm. Three fast-time simulation expe...
Bird strikes have the potential to cause severe damage to aircraft. Therefore, measures to reduce... more Bird strikes have the potential to cause severe damage to aircraft. Therefore, measures to reduce the risk of bird strikes are performed at airports. However, this risk is not limited to the airport but is increased in the arrival and departure corridors as well. Consequently, a significant amount of bird strikes occurs outside the direct airport area. To estimate the risk of bird strikes in this extended airport area, a fast-time simulation environment was developed, representing air traffic as well as bird movement. It was verified by performing Monte-Carlo Simulations including real flight plans, a model for realistic bird movements and a comparison to real bird strike data. In this study, the simulation results were evaluated considering the impact of bird strikes. For this purpose, the kinetic energy of the bird strikes that occurred within the simulation was calculated. Based on the international certification requirements for the impact resistance of engines, windshields and ...
The aerodynamic properties of an aircraft determine a crucial part of the aircraft performance mo... more The aerodynamic properties of an aircraft determine a crucial part of the aircraft performance model. Deriving accurate aerodynamic coefficients requires detailed knowledge of the aircraft’s design. These designs and parameters are well protected by aircraft manufacturers. They rarely can be used in public research. Very detailed aerodynamic models are often not necessary in air traffic management related research, as they often use a simplified point-mass aircraft performance model. In these studies, a simple quadratic relation often assumed to compute the drag of an aircraft based on the required lift. This so-called drag polar describes an approximation of the drag coefficient based on the total lift coefficient. The two key parameters in the drag polar are the zero-lift drag coefficient and the factor to calculate the lift-induced part of the drag coefficient. Thanks to this simplification of the flight model together with accurate flight data, we are able to estimate these aero...
This document describes the context required to generate the scenarios for the batch simulations.... more This document describes the context required to generate the scenarios for the batch simulations. It is based on a review of literature on: - Demographics & urbanisation - Transport & Energy - UAVs (suitable for the urban environment) - Personal Air vehicles (as suitable for the urban environment) - Communication, Navigation & Surveillance system requirements - Infrastructure Requirements The focus is on the city 50+ years into the future. The current status and trends of the development of urbanisation and mobility will be extrapolated to the future. This gives the estimate for the future demand, both qualitatively (which applications) and quantitatively. For UAVs there already are vehicles available, which can be used for urban cargo transport. A review of existing (proto)types has been performed. Based on the expected demand and expected technological advances, the future cargo UAV and its application will be described. A review of on-going developments on personal air transport ...
Transportation Research Part C: Emerging Technologies, 2018
This paper presents analytical models that describe the safety of unstructured and layered en rou... more This paper presents analytical models that describe the safety of unstructured and layered en route airspace designs. Here, 'unstructured airspace' refers to airspace designs that offer operators complete freedom in path planning, whereas 'layered airspace' refers to airspace concepts that utilize heading-altitude rules to vertically separate cruising aircraft based on their travel directions. With a focus on the intrinsic safety provided by an airspace design, the models compute instantaneous conflict counts as a function of traffic demand and airspace design parameters, such as traffic separation requirements and the permitted heading range per flight level. While previous studies have focused primarily on conflicts between cruising aircraft, the models presented here also take into account conflicts involving climbing and descending traffic. Fasttime simulation experiments used to validate the modeling approach indicate that the models estimate instantaneous conflict counts with high accuracy for both airspace designs. The simulation results also show that climbing and descending traffic caused the majority of conflicts for layered airspaces with a narrow heading range per flight level, highlighting the importance of including all aircraft flight phases for a comprehensive safety analysis. Because such trends could be accurately predicted by the three-dimensional models derived here, these analytical models can be used as tools for airspace design applications as they provide a detailed understanding of the relationships between the parameters that influence the safety of unstructured and layered airspace designs.
This investigation has been carried out partly under a contract awarded by the Netherlands Depart... more This investigation has been carried out partly under a contract awarded by the Netherlands Department of Civil Aviation (RLD) , contract number OV/RLD-690. The RLD has granted NLR permission to publish this report. The contents of this report may be cited on condition that full credit is given to NLR and the authors.
Most Free-Flight concepts rely on self-separation by means of airborne Conflict Detection and Res... more Most Free-Flight concepts rely on self-separation by means of airborne Conflict Detection and Resolution (CD&R) algorithms. A key enabling technology for airborne CD&R is the Automatic Dependent Surveillance-Broadcast (ADS-B) system, which is used for direct state information exchange between aircraft. Similar to other communication systems, ADS-B is affected by a number of limitations which can be broadly classified as system and situation related deficiencies. This re- search investigates the impact of these limitations on the viability of using ADS-B for airborne CD&R within the Free-Flight context. Here, ‘state-based’ conflict detection and the modified voltage potential conflict resolution algorithm are used as a case- study. An ADS-B model is developed, and its effect on the aforementioned CD&R method is measured using three fast- time simulation experiments. The experiments studied overall safety with ADS-B, as well as the specific effect of situation related characteristics,...
This paper describes the initial results of a simulation experiment in which the human factors im... more This paper describes the initial results of a simulation experiment in which the human factors implications of three Mixed Equipage, Integrated Air-Ground, Free Flight Air Traffic Management (ATM) scenarios were investigated. The experiment primarily addressed how to accommodate a fleet of mixed equipped aircraft, with and without Airborne Separation Assurance System (ASAS), in a transitional free flight era in which both air and ground players have defined responsibilities. All three transitional ATM operational concepts evaluated, were designed with the idea that equipping aircraft should be immediately beneficial to the airlines.
Le Centre pour la Communication Scientifique Directe - HAL - memSIC, Oct 19, 2022
Many services have a complex network infrastructure (transport, Internet, etc.). Disruptions caus... more Many services have a complex network infrastructure (transport, Internet, etc.). Disruptions caused by accidents or weather conditions can paralyze traffic for a long time. But how to improve the robustness of networks? This robustness improvement would reduce the time of exposure to disruptions and their impact on overall traffic. Lots of studies have been done on identifying critical links and nodes but not so many analyze the paths. In this paper, we propose a new method to measure network robustness based on alternative paths. Beyond improving the French low-cost flight network robustness by 15%, the method attempts to show the relevance of analyzing network vulnerability from a path-based approach.
The presented research evaluates the concept of providing an airport’s Air Traffic Control with a... more The presented research evaluates the concept of providing an airport’s Air Traffic Control with a bird strike advisory system. Such a system informs the controller about current and predicted bird movements in the arrival and departure corridors. Based on this information, the controller can decide to delay or reroute air traffic in order to prevent collisions with birds. To evaluate the resulting effects on the airport’s safety and capacity, fast-time simulations merging air traffic and bird movements, will be performed. To represent realistic bird movements, inputs from two different radar types are combined. For the close airport environment, historic bird tracks from avian radar installed at the considered airport serve as source. To cover the arrival and departure corridors up to 3000ft, the altitude up to which the largest majority of bird strikes occur, data from weather radar is used: based on bird densities and speed directions, bird tracks are generated for different altitude bands. The obtained tracks from avian and weather radar are combined in order to retrieve the overall image of bird movements in the close and extended airport area. This paper describes the methods for extracting, generating and finally combining the inputs from the two radar sources, in order to generate realistic bird movements. These will serve as a key input parameter for evaluating the effects of a bird strike advisory system with fast-time simulations.
Current investigations into urban aerial mobility, as well as the continuing growth of global air... more Current investigations into urban aerial mobility, as well as the continuing growth of global air transportation, have renewed interest in Conflict Detection and Resolution (CD&R) methods. With the new applications of drones, and the implications of a profoundly different urban airspace, new demands are placed on such algorithms, further spurring new research. This paper presents a review of current CR methods for both manned and unmanned aviation. It presents a taxonomy that categorises algorithms in terms of their approach to avoidance planning, surveillance, control, trajectory propagation, predictability assumption, resolution manoeuvre, multi-actor conflict resolution, considered obstacle types, optimization, and method category. More than a hundred CR methods were considered, showing how most work on a tactical, distributed framework. To enable a reliable comparison between methods, this paper argues that an open and ideally common simulation platform, common test scenarios, and common metrics are required. This paper presents an overview of four CR algorithms, each representing a commonly used CR algorithm category. Both manned and unmanned scenarios were tested, through fast-time simulations on an open-source airspace simulation platform.
How should traffic be structured to handle high density PAV/UAV traffic over urban areas? Four di... more How should traffic be structured to handle high density PAV/UAV traffic over urban areas? Four different Airspace designs are developed and evaluated concerning capacity, robustness, efficiency and safety.
The interest in urban air mobility as a potential solution for urban congestion is steadily growi... more The interest in urban air mobility as a potential solution for urban congestion is steadily growing. Air operations in urban areas can present added complexity as compared with traditional air traffic management. As a result, it is necessary to test and develop novel airspace designs and rules. As airspace in urban areas is a scarce resource, creating structures and rules that effectively utilise the airspace is an important challenge. This work specifically focuses on layered airspace design in urban operations constrained to fly between the existing buildings. Two design parameters of airspace design are investigated with two sub-experiments. Sub-experiment 1 investigates layer function assignment by comparing concepts from previous research with different layer assignment distributions. Sub-experiment 2 investigates the flight rules of vertical distribution of traffic within the airspace, to determine whether this is best achieved in a static (pre-allocated) or dynamic manner. Bo...
This paper presents an analysis of the potential fuel and emission benefits of implementing Conti... more This paper presents an analysis of the potential fuel and emission benefits of implementing Continuous Descent Operations at Schiphol International Airport, from cruise altitude to the final approach fix, for a large scope of aircraft types. Using historical data from on-board sources and ADS-B, fuel-optimal continuous descents are simulated using the total-energy model. By comparing the fuel consumption between historical flights and the simulated continuous descent flights, fuel benefits are found. CO2 emissions are then calculated linearly from the fuel benefits. The results show average savings of 92kg up to 500 kg of fuel per flight. For Schiphol, this results in a total of 39 million kg of fuel savings per, year leading to more than 123 thousand tonnes of CO2 savings per year.
This paper focuses on estimating aircraft mass and thrust setting using a recursive Bayesian meth... more This paper focuses on estimating aircraft mass and thrust setting using a recursive Bayesian method called particle filtering. The method is based on a nonlinear state-space system derived from aircraft point-mass performance models. Using solely ADS-B and Mode-S data, flight states such as position, velocity, and wind speed are collected and used for the estimation. An important aspect of particle filtering is noise modeling. Four noise models are proposed in this paper based on the native ADS-B Navigation Accuracy Category (NAC) parameters. Simulations, experiments, and validation, based on a number of flights are carried out to test the theory. As a result, convergence of the estimation can usually be obtained within 30 seconds for any climbing flight. The method proposed in this paper not only provides final estimates, but also defines the limits of noise above which estimation of mass and thrust becomes impossible. When validated with a dataset consisting of the measured true m...
How should traffic be structured to handle high density PAV/UAV traffic over urban areas? Four di... more How should traffic be structured to handle high density PAV/UAV traffic over urban areas? Four different Airspace designs are developed and evaluated concerning capacity, robustness, efficiency and safety.
The world population is expected to grow further with a major increase in population living in ur... more The world population is expected to grow further with a major increase in population living in urban areas. Exploiting the door-to-door concept to the full extent, a considerable part of conventional vehicles may be replaced by personal aerial vehicles. Cargo delivery system will the follow same philosophy using unmanned aerial vehicles. This brings up completely new challenges for future air traffic management in urban environments. The Metropolis research project investigates radically new airspace design concepts for the urban environments 50+ years into the future, which are extreme when compared to today in terms of traffic density, complexity and constraints. This work presents the results of simulation data analysis and a comparison of concepts of urban airspace design regarding organizational (complexity) metrics. The aim was to identify how the structure involved in the concept of urban airspace design influences the complexity of the traffic situation. In this work geometr...
This paper presents a semi-empirical method to determine the maximum theoretical capacity of dece... more This paper presents a semi-empirical method to determine the maximum theoretical capacity of decentralized airspace concepts. The method considered here, named Capacity Assessment Method for Decentralized ATC (CAMDA), formalizes an earlier approach described in literature, extends it for threedimensional airspace, and also improves the accuracy of the underlying models. CAMDA defines capacity as the traffic density at which conflict chain reactions propagate uncontrollably throughout the entire airspace. CAMDA identifies this critical density using a semi-empirical approach whereby models describing the actions of decentralized conflict detection and resolution algorithms are combined with empirically obtained conflict count data. The CAMDA method is demonstrated in this work for a decentralized direct routing en-route airspace concept that utilizes a state-based conflict detection algorithm, and a voltage potentialbased conflict resolution algorithm. Three fast-time simulation expe...
Bird strikes have the potential to cause severe damage to aircraft. Therefore, measures to reduce... more Bird strikes have the potential to cause severe damage to aircraft. Therefore, measures to reduce the risk of bird strikes are performed at airports. However, this risk is not limited to the airport but is increased in the arrival and departure corridors as well. Consequently, a significant amount of bird strikes occurs outside the direct airport area. To estimate the risk of bird strikes in this extended airport area, a fast-time simulation environment was developed, representing air traffic as well as bird movement. It was verified by performing Monte-Carlo Simulations including real flight plans, a model for realistic bird movements and a comparison to real bird strike data. In this study, the simulation results were evaluated considering the impact of bird strikes. For this purpose, the kinetic energy of the bird strikes that occurred within the simulation was calculated. Based on the international certification requirements for the impact resistance of engines, windshields and ...
The aerodynamic properties of an aircraft determine a crucial part of the aircraft performance mo... more The aerodynamic properties of an aircraft determine a crucial part of the aircraft performance model. Deriving accurate aerodynamic coefficients requires detailed knowledge of the aircraft’s design. These designs and parameters are well protected by aircraft manufacturers. They rarely can be used in public research. Very detailed aerodynamic models are often not necessary in air traffic management related research, as they often use a simplified point-mass aircraft performance model. In these studies, a simple quadratic relation often assumed to compute the drag of an aircraft based on the required lift. This so-called drag polar describes an approximation of the drag coefficient based on the total lift coefficient. The two key parameters in the drag polar are the zero-lift drag coefficient and the factor to calculate the lift-induced part of the drag coefficient. Thanks to this simplification of the flight model together with accurate flight data, we are able to estimate these aero...
This document describes the context required to generate the scenarios for the batch simulations.... more This document describes the context required to generate the scenarios for the batch simulations. It is based on a review of literature on: - Demographics & urbanisation - Transport & Energy - UAVs (suitable for the urban environment) - Personal Air vehicles (as suitable for the urban environment) - Communication, Navigation & Surveillance system requirements - Infrastructure Requirements The focus is on the city 50+ years into the future. The current status and trends of the development of urbanisation and mobility will be extrapolated to the future. This gives the estimate for the future demand, both qualitatively (which applications) and quantitatively. For UAVs there already are vehicles available, which can be used for urban cargo transport. A review of existing (proto)types has been performed. Based on the expected demand and expected technological advances, the future cargo UAV and its application will be described. A review of on-going developments on personal air transport ...
Transportation Research Part C: Emerging Technologies, 2018
This paper presents analytical models that describe the safety of unstructured and layered en rou... more This paper presents analytical models that describe the safety of unstructured and layered en route airspace designs. Here, 'unstructured airspace' refers to airspace designs that offer operators complete freedom in path planning, whereas 'layered airspace' refers to airspace concepts that utilize heading-altitude rules to vertically separate cruising aircraft based on their travel directions. With a focus on the intrinsic safety provided by an airspace design, the models compute instantaneous conflict counts as a function of traffic demand and airspace design parameters, such as traffic separation requirements and the permitted heading range per flight level. While previous studies have focused primarily on conflicts between cruising aircraft, the models presented here also take into account conflicts involving climbing and descending traffic. Fasttime simulation experiments used to validate the modeling approach indicate that the models estimate instantaneous conflict counts with high accuracy for both airspace designs. The simulation results also show that climbing and descending traffic caused the majority of conflicts for layered airspaces with a narrow heading range per flight level, highlighting the importance of including all aircraft flight phases for a comprehensive safety analysis. Because such trends could be accurately predicted by the three-dimensional models derived here, these analytical models can be used as tools for airspace design applications as they provide a detailed understanding of the relationships between the parameters that influence the safety of unstructured and layered airspace designs.
This investigation has been carried out partly under a contract awarded by the Netherlands Depart... more This investigation has been carried out partly under a contract awarded by the Netherlands Department of Civil Aviation (RLD) , contract number OV/RLD-690. The RLD has granted NLR permission to publish this report. The contents of this report may be cited on condition that full credit is given to NLR and the authors.
Most Free-Flight concepts rely on self-separation by means of airborne Conflict Detection and Res... more Most Free-Flight concepts rely on self-separation by means of airborne Conflict Detection and Resolution (CD&R) algorithms. A key enabling technology for airborne CD&R is the Automatic Dependent Surveillance-Broadcast (ADS-B) system, which is used for direct state information exchange between aircraft. Similar to other communication systems, ADS-B is affected by a number of limitations which can be broadly classified as system and situation related deficiencies. This re- search investigates the impact of these limitations on the viability of using ADS-B for airborne CD&R within the Free-Flight context. Here, ‘state-based’ conflict detection and the modified voltage potential conflict resolution algorithm are used as a case- study. An ADS-B model is developed, and its effect on the aforementioned CD&R method is measured using three fast- time simulation experiments. The experiments studied overall safety with ADS-B, as well as the specific effect of situation related characteristics,...
This paper describes the initial results of a simulation experiment in which the human factors im... more This paper describes the initial results of a simulation experiment in which the human factors implications of three Mixed Equipage, Integrated Air-Ground, Free Flight Air Traffic Management (ATM) scenarios were investigated. The experiment primarily addressed how to accommodate a fleet of mixed equipped aircraft, with and without Airborne Separation Assurance System (ASAS), in a transitional free flight era in which both air and ground players have defined responsibilities. All three transitional ATM operational concepts evaluated, were designed with the idea that equipping aircraft should be immediately beneficial to the airlines.
Le Centre pour la Communication Scientifique Directe - HAL - memSIC, Oct 19, 2022
Many services have a complex network infrastructure (transport, Internet, etc.). Disruptions caus... more Many services have a complex network infrastructure (transport, Internet, etc.). Disruptions caused by accidents or weather conditions can paralyze traffic for a long time. But how to improve the robustness of networks? This robustness improvement would reduce the time of exposure to disruptions and their impact on overall traffic. Lots of studies have been done on identifying critical links and nodes but not so many analyze the paths. In this paper, we propose a new method to measure network robustness based on alternative paths. Beyond improving the French low-cost flight network robustness by 15%, the method attempts to show the relevance of analyzing network vulnerability from a path-based approach.
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