European Airspace Research Articles

Increasing airspace capacity by improving ATCo’s efficiency through an innovative handover mechanism

The current lack of airspace capacity poses a major challenge to a sustainable and efficient air transport system, especially as future demand increases. Recent efforts to increase airspace capacity have focused on airspace sectorization. The digitization of Air Traffic Management (ATM) holds promise for overcoming current inefficiencies arising from the spatial fragmentation of airspace. While research has explored digitized ATM services to improve airspace capacity, there has been a notable gap in addressing spare capacity through enhancing synergies between adjacent sectors. This work proposes the application of an early handover (EHO) mechanism based on the spatio-temporal interdependencies among sectors and aircraft. Essentially, the mechanism involves alleviating overloaded sectors by redistributing peak demand to neighboring ones. This alleviation results in a reduction of the dedicated resources required to meet demand, facilitating the consolidation of sectors into larger units. Ultimately, this consolidation enhances airspace efficiency by minimizing the ATCo resources necessary for ATM. A simple and fast heuristic is proposed to select the aircraft for early handover to the air traffic controller of another sector, together with a specific schedule. A Colored Petri Net model is implemented to formalize the dynamic spatio-temporal interdependencies among adjacent sectors and to illustrate the EHO applicability using an academic exercise for illustration purposes. Afterwards, a simulation study based on real European airspace data is employed to illustrate and validate the mechanism. Finally, a discussion on the potential impacts of adopting the mechanism in real-life applications and lines of future research are provided.

Characterization of Strategic Deconflicting Service Impact on Very Low-Level Airspace Capacity

European airspace is poised for significant transformation as it prepares to accommodate a new class of unmanned traffic that will reshape the transport of people and goods. Unmanned aerial vehicle traffic will introduce a new level of services, but it remains unclear how safety and operators’ time flexibility in flight planning will impact capacity. This study focuses on the impact of strategic deconflicting services on the capacity of the very low-level airspace, a critical area in the future management of unmanned aerial vehicle traffic. The results validate the assumptions regarding the roles of airspace managers and drone operators through simulation studies; highlight the limitations of the first come, first served policy; and propose a batch policy as a potential optimization strategy for future airspace capacity management. The forecasting model developed using regression techniques provides a general method for predicting airspace capacity under specific conditions, contributing to the safe and efficient integration of unmanned aerial vehicles into European airspace.

Visual analysis of changes in European air transport during the COVID-19 pandemic from interactive maps

Abstract The paper explores the substantial decline in European air transport during 2020, while employing interactive maps for visual analysis. According to the International Civil Aviation Organization’s (2020) economic analysis, there was a sharp 60% global reduction in passenger traffic during the combined second, third, and fourth quarters, equivalent to about 2.7 billion fewer passengers than in 2019. The established air traffic flow, which developed over decades, faced partial disruption due to COVID-19 restrictions. Consequently, the aviation industry strategically focused on restructuring to ensure the sustained operation of major air transport routes. Using OpenSky Network data and a Google Sheets environment for storage, our study utilizes the FlowmapBlue interactive platform to visualize the 2020 European airspace, and to define key air traffic corridors. Despite the substantial decline, the visualization reveals resilient routes and crucial connections, underscoring the imperative of preserving these links for effective crisis response in the future.

Interoperable data exchange for safe and efficient launch and re-entry operations in an international environment

The frequency of commercial space launch and re-entry operations is increasing worldwide. Current regulations and procedures ensure safe operations by temporarily closing large volumes of airspace where risks to aircraft would exist in case of non-nominal events during launch or re-entry operations. To maintain the safety of air traffic as the number of space operations rises, effectively providing the right information to the right stakeholders at the right time is key. Through a cooperative agreement, the FAA and DLR are sharing their unique capabilities using the Commercial Space Integration Lab and Air Traffic Validation Center, located in the USA and Germany respectively, to improve situational awareness through real-time data exchange. The project seeks to answer whether U.S. and European ANSPs can respond adequately to a non-nominal event during a launch or re-entry operation that presents a hazard to the airspace system. It leverages existing international data standards and infrastructures by using a data exchange approach based on System Wide Information Management (SWIM). Within the project an initial assessment of the processes, roles and responsibilities for implementing launch and re-entry events in the air traffic systems on both sides of the Atlantic, as well as the requirements for basic functions and performance parameters of a SWIM-based integration, have been completed. The project developed a demonstration model across all system levels as far down as to the ANSPs, namely to the air traffic controllers. Through a series of demonstrations, covering launch scenarios from the U.S. with possible effects on European airspace and vice versa, the project evaluated the technical and operational feasibility of the concept. The key data parameters identified during the analyses shall enable information sharing among various users within the U.S. and European global airspace system. It has been shown, that the systems on both sides of the Atlantic could be connected via standardized protocols und used successfully for exercises in different scenarios. Further research on the best integration of the processes in international Air Traffic Management (ATM) networks and domains will be the follow-on.

A STAM Model Based on Spatiotemporal Airspace Sector Interdependencies to Minimize Tactical Flow Management Regulations

The lack of airspace capacity poses a significant challenge for a sustainable air transport system, particularly in scenarios of future growing demand. Air traffic management digitalization opens pathways for innovative and efficient solutions to tackle existing inefficiencies arising from spatially fragmented airspace. While research has focused on digitalized ATM services to improve airspace capacity, synergies among adjacent sectors to utilize latent capacity remain unexplored. Using a sector network model, in this study, we analyze spatiotemporal sector interdependencies, quantify time-stamp topological interdependencies, and evaluate capacity enhancement possibilities for sectors unable to meet dynamic demand. The occupancy count dynamic evolution and poor correlation among the over-loaded sectors with the occupancy count of its adjacent sectors provide opportunities for a short-term ATM mechanism, ensuring sector-level capacity invulnerability and enhancing airspace capacity at the network level. A computational experiment using real data from the European airspace is carried out to illustrate and validate this innovative solution.

Leveraging demand-capacity balancing to reduce air traffic emissions and improve overall network performance

Improvements in European air traffic management (ATM) constitute one of the key levers to reduce aviation emissions in the future to reach ambitious goals. In this paper, we evaluate the benefits of improved network-centric ATM with coordinated optimisation of capacity, delays, re-routings and emissions vs the present fragmented ATM which has generated high delays and extensive re-routing due to sub-optimal capacity provision. In addition, we analyse the impact on flight efficiency of a novel trajectory-independent airport-pair charging scheme, which makes shortest routes the cheapest for Airspace Users (AUs), which is not always the case with the current charging scheme in Europe. We test and evaluate proposed changes in ATM using a case study based on real data covering 3,000–4,000 flights in large parts of Western European airspace. We find that network-centric ATM can reduce variable costs borne by AUs by 21% and in particular re-routing cost (and associated emissions) by almost 64%. Furthermore, airport-pair charging can save almost 11% of costs for AUs and up to 320,000 tons of CO2 emissions — if accompanied by adequate capacity changes that reflect the shift in demand towards shorter trajectories. We conclude that various stakeholder initiatives to reduce the fragmentation in European ATM and to move towards a more network-centric approach have merits and should be pursued by the policy makers.

Cross-Border Capacity Planning in Air Traffic Management Under Uncertainty

In European air traffic management (ATM), it is an important decision how much capacity to provide for each airspace, and it has to be made weeks or even months in advance of the day of operation. Given the uncertainty in demand that may materialize until then along with variability in capacity provision (e.g., due to weather), Airspace Users could face high costs of displacements (i.e., delays and reroutings) if capacity is not provided where and when needed. We propose a new capacity sharing scheme in which some proportion of overall capacities can be flexibly deployed in any of the airspaces of the same alliance (at an increased unit cost). This allows us to hedge against the risk of capacity underprovision. Given this scheme, we seek to determine the optimum budget for capacities provided both locally and in cross-border sharing that results in the lowest expected network costs (i.e., capacity and displacement costs). To determine optimum capacity levels, we need to solve a two-stage newsvendor problem: We first decide on capacities to be provided for each airspace, and after uncertain demand and capacity provision disruptions have materialized, we need to decide on the routings of flights (including delays) as well as the sector opening scheme of each airspace to minimize costs. We propose a simulation optimization approach for searching the most cost-efficient capacity levels (in the first stage), and a heuristic to solve the routing and sector opening problem (in the second stage), which is [Formula: see text]-hard. We test our approach in a large-sized simulation study based on real data covering around 3,000 flights across Western European airspace. We find that our stochastic approach significantly reduces network costs against a deterministic benchmark while using less computational resources. Experiments on different setups for capacity sharing show that total variable costs can be reduced by more than 8% if capacity is shared across borders: even though we require that no airspace can operate lower capacities under capacity sharing than without (this is to avoid substitution of expensive air traffic controllers with those in countries with a lower wage level). We also find that the use of different technology providers is a major obstacle to reap the benefits from capacity sharing and that sharing capacities across airspaces of the same country may instead be preferred. History: This paper has been accepted for the Transportation Science Special Issue on Emerging Topics in Transportation Science and Logistics. Funding: This work was supported by the Horizon 2020 Framework Programme [893380]. Supplemental Material: The online appendix is available at https://doi.org/10.1287/trsc.2023.1210 .

Systemic risks perspectives of Eyjafjallajökull volcano's 2010 eruption

In 2010, southern Iceland's Eyjafjallajökull volcano erupted, releasing ash that spread across Europe. Due to its potential to damage aircraft, much of European airspace was closed for six days. Known problems were brought to the forefront regarding the anticipation of and response to systemic risks. To contribute a deeper understanding of this situation, this paper explores this disaster through its fundamental causes and cascading impacts, highlighting perspectives from disaster risk reduction, complexity sciences, and health in order to support analysis and resolution of systemic risks. Two principal future directions emerge from this work. First, how to manage dependency on air travel. Second, how to think about and act to avert future calamities.

Propagation of Interactions among Aircraft Trajectories: A Complex Network Approach

Interactions between aircraft, as, e.g., those caused by minimum separation infringements, can trigger non-local cascades of interactions that can propagate over large temporal and spatial scales. Assessing those downstream effects is a computationally complex problem, which has only been tackled over rather limited time horizons. We here propose a methodology to map these interactions into networks, thus representing their potential propagation and the structure induced by them. The result is a conceptually simple and computationally tractable representation, which can be further analyzed using metrics provided by a complex networks theory. We firstly test this methodology using a synthetic airspace, then move on to the analysis of planned and executed trajectories for a large European airspace in the year 2018. We show how these propagation networks reflect the structure of airways, the intervention of air traffic controllers, and how they have evolved through time. We finally discuss potential real-world applications, and some key aspects that need to be further studied to make this a viable instrument in an operational context.

Flight Training Syllabus Structure Impact on Proactive Planning of High-Performance Military Aircraft Pilot Training Operations in Flexible Airspace Structures

European airspace is marked by fragmentation, and from fragmentation originated congestion. As an answer to congestion, flexible use of airspace is created to fulfil all users’ requirements optimally, and at its very core lies civil-military cooperation and the coordination of airspace use. Such an approach is enabled by collaborative decision-making, which presumes timely and complete exchange of complete relevant information between airspace users. To participate in the process, the military should be transparent regarding its restrictions and capabilities of adaptation to other airspace users’ demands. Flight training syllabus structure and its specific impact on proactive planning of high-performance military aircraft pilot training operations in flexible airspace structures is the subject of this research. Significant diversity in the hourly distribution of civil traffic demand in flexible airspace structures in Zagreb FIR proves them applicable for a proactive approach to high-performance aircraft pilot training operations planning and management. Noticeable reduction in the number of civil aircraft affected by high-performance aircraft pilot training operations in flexible airspace structures at congested flight levels is corroborated. Simulations of proactive planning of high-performance aircraft pilot training operations reveal indications of flight syllabus structure’s impact on pilot flight training duration, as well as the possibility to manage its restrictions.

Implementation and Real-Time Validation of a European Remain Well Clear Function for Unmanned Vehicles

The full integration of Remotely Piloted unmanned vehicles into civil airspace requires first and foremost the integration of a traffic Detect and Avoid (DAA) system into the vehicle. The DAA system supports remote pilots in performing their task of remaining Well Clear from other aircraft and avoiding collisions. Several studies related to the design of a Remain Well Clear function have been performed that served as input for the development of technical standards applicable to non-European countries. In this paper, a Remain Well Clear implementation is proposed that, using the results of past international projects, fits European airspace needs and specificities and can be acceptable to both remote pilots and air traffic controllers, with only minimal impact on the standard operating procedures used for manned aircraft. The proposed Remain Well Clear software has been successfully validated through real-time simulations with pilots and controllers in the loop considering traffic encounters and mission scenarios typically found in European airspace. The achieved results highlight the appropriate situational awareness provided by the proposed RWC function and its effective support to the remote pilot in making adequate decisions in conflict solving. Real-time simulation tests showed that, in almost all cases, an RWC maneuver is successfully performed, giving the RP sufficient time to assess the conflict, coordinate with the controller, if needed, and execute the maneuver. The fundamental role of the proposed RWC function has been especially evident in uncontrolled airspace classes where the controller does not provide any separation provision. Moreover, its effectiveness has also been tested in encounters with aircraft flying under visual flight rules in controlled airspace, where the controller is not informed or has less information regarding these aircraft. The results from validation tests imply two key potential safety benefits, namely: the mitigation of performing a collision avoidance maneuver and the prevention of potential conflict while not disrupting the traffic flow with possible further consequences of generating other potentially hazardous situations.

Augmented Air Traffic Control System—Artificial Intelligence as Digital Assistance System to Predict Air Traffic Conflicts

Today’s air traffic management (ATM) system evolves around the air traffic controllers and pilots. This human-centered design made air traffic remarkably safe in the past. However, with the increase in flights and the variety of aircraft using European airspace, it is reaching its limits. It poses significant problems such as congestion, deterioration of flight safety, greater costs, more delays, and higher emissions. Transforming the ATM into the “next generation” requires complex human-integrated systems that provide better abstraction of airspace and create situational awareness, as described in the literature for this problem. This paper makes the following contributions: (a) It outlines the complexity of the problem. (b) It introduces a digital assistance system to detect conflicts in air traffic by systematically analyzing aircraft surveillance data to provide air traffic controllers with better situational awareness. For this purpose, long short-term memory (LSTMs) networks, which are a popular version of recurrent neural networks (RNNs) are used to determine whether their temporal dynamic behavior is capable of reliably monitoring air traffic and classifying error patterns. (c) Large-scale, realistic air traffic models with several thousand flights containing air traffic conflicts are used to create a parameterized airspace abstraction to train several variations of LSTM networks. The applied networks are based on a 20–10–1 architecture while using leaky ReLU and sigmoid activation function. For the learning process, the binary cross-entropy loss function and the adaptive moment estimation (ADAM) optimizer are applied with different learning rates and batch sizes over ten epochs. (d) Numerical results and achievements by using LSTM networks to predict various weather events, cyberattacks, emergency situations and human factors are presented.

Geospatial technologies for an automated holistic risk assessment of UAS operations

Abstract. The rising number of UAS operations in the European airspace poses a safety issue. The key problem is to ensure safe drone traffic management and their integration into the existing air traffic environment. Thus, risk assessment becomes an integral part of every UAS operation and its automation is of great importance when dealing with growing numbers of flights. There exist many attempts to support such risk assessment, but an optimal solution is yet to be found. This paper presents a prototype of a web application, which automates strategic risk assessment of open and specific UAS operations in Austria with the use of open government geodata. Risk assessment results are visualized on a map, showing spatial distribution of classified risks in the operational area. This prototype is the first attempt to combine the functions of a “drone map” representing relevant geodata and a questionnaire usually used to support specific operation risk assessment. There is a potential to turn it into a tool which is used to create a comprehensive pre-flight safety portfolio or to support the automatic risk assessment performed by a UTM before a UAS operation is checked in. Simplifying the creation of safety portfolios and automating UAS operation risk assessment are important factors in promoting a wider and safer use of UAS.

Harmonization and Verification of Three National European Icing Forecast Models Using Pilot Reports

The Single European Sky Air Traffic Management Research (SESAR) program aims at modernizing and harmonizing the European airspace, which currently has a strongly fragmented character. Besides turbulence and convection, in-flight icing is part of SESAR and can be seen as one of the most important meteorological phenomena, which may lead to hazardous flight conditions for aircraft. In this study, several methods with varying complexities are analyzed for combining three individual in-flight icing forecasts based on numerical weather prediction models from Deutscher Wetterdienst, Météo-France, and Met Office. The optimal method will then be used to operate one single harmonized in-flight icing forecast over Europe. As verification data, pilot reports (PIREPs) are used, which provide information about hazardous weather and are currently the only direct regular measure of in-flight icing events available. In order to assess the individual icing forecasts and the resulting combinations, the probability of detection skill score is calculated based on multicategory contingency tables for the forecast icing intensities. The scores are merged into a single skill score to give an overview of the quality of the icing forecast and enable comparison of the different model combination approaches. The concluding results show that the most complex combination approach, which uses iteratively optimized weighting factors for each model, provides the best forecast quality according to the PIREPs. The combination of the three icing forecasts results in a harmonized icing forecast that exceeds the skill of each individual icing forecast, thus providing an improvement to in-flight icing forecasts over Europe.

A Spatially Bounded Airspace Axiom

Free Route Airspace (FRA), a new concept implemented across European airspace, is designed to eliminate the adverse effects of air traffic, reduce fuel consumption, simplify and expand flight planning. In our research, we model FRA system by using graph theory and we use networks and convex analysis to study it. We work with 2-dimensional space defined by latitude a longitude. We know that the basic mathematical properties of a scientific discipline can be expressed using mathematical axioms. Therefore, in our work, we sought to answer the question, what are the basic mathematical properties of airspace? We found a mathematical object that can describe airspace in general. Using this object, we uttered an axiom describing airspace. Our axiom is given by means of practical, significant entry and entry-exit points in the airspace.

Case Study for Testing the Validity of NOx-Ozone Algorithmic Climate Change Functions for Optimising Flight Trajectories

One possibility to reduce the climate impact of aviation is the avoidance of climate-sensitive regions, which is synonymous with climate-optimised flight planning. Those regions can be identified by algorithmic Climate Change Functions (aCCFs) for nitrogen oxides (NOx), water vapour (H2O) as well as contrail cirrus, which provide a measure of climate effects associated with corresponding emissions. In this study, we evaluate the effectiveness of reducing the aviation-induced climate impact via ozone (O3) formation (resulting from NOx emissions), when solely using O3 aCCFs for the aircraft trajectory optimisation strategy. The effectiveness of such a strategy and the associated potential mitigation of climate effects is explored by using the chemistry–climate model EMAC (ECHAM5/MESSy) with various submodels. A summer and winter day, characterised by a large spatial variability of the O3 aCCFs, are selected. A one-day air traffic simulation is performed in the European airspace on those selected days to obtain both cost-optimised and climate-optimised aircraft trajectories, which more specifically minimised a NOx-induced climate effect of O3 (O3 aCCFs). The air traffic is laterally and vertically re-routed separately to enable an evaluation of the influences of the horizontal and vertical pattern of O3 aCCFs. The resulting aviation NOx emissions are then released in an atmospheric chemistry–climate simulation to simulate the contribution of these NOx emissions to atmospheric O3 and the resulting O3 change. Within this study, we use O3-RF as a proxy for climate impact. The results confirm that the climate-optimised flights lead to lower O3-RF compared to the cost-optimised flights, although the aCCFs cannot reproduce all aspects of the significant impact of the synoptic situation on the transport of emitted NOx. Overall, the climate impact is higher for the selected summer day than for the selected winter day. Lateral re-routing shows a greater potential to reduce climate impact compared to vertical re-routing for the chosen flight altitude. We find that while applying the O3 aCCFs in trajectory optimisation can reduce the climate impact, there are certain discrepancies in the prediction of O3 impact from aviation NOx emissions, as seen for the summer day. Although the O3 aCCFs concept is a rough simplification in estimating the climate impact of a local NOx emission, it enables a reasonable first estimate. Further research is required to better describe the O3 aCCFs allowing an improved estimate in the Average Temperature Response (ATR) of O3 from aviation NOx emissions. A general improvement in the scientific understanding of non-CO2 aviation effects could make climate-optimised flight planning practically feasible.

Analysis of the Structure and Dynamics of European Flight Networks

We analyze structure and dynamics of flight networks of 50 airlines active in the European airspace in 2017. Our analysis shows that the concentration of the degree of nodes of different flight networks of airlines is markedly heterogeneous among airlines reflecting heterogeneity of the airline business models. We obtain an unsupervised classification of airlines by performing a hierarchical clustering that uses a correlation coefficient computed between the average occurrence profiles of 4-motifs of airline networks as similarity measure. The hierarchical tree is highly informative with respect to properties of the different airlines (for example, the number of main hubs, airline participation to intercontinental flights, regional coverage, nature of commercial, cargo, leisure or rental airline). The 4-motif patterns are therefore distinctive of each airline and reflect information about the main determinants of different airlines. This information is different from what can be found looking at the overlap of directed links.

Cross-border Free Route Airspace concept and its impact on flight efficiency improvement

The implementation of Free Route Airspace (FRA) in European Airspace has significantly reduced flight distances. However, there are still elements in the conventional FRA that need to be optimized in order to allow a further improvement in flight efficiency and these are the predefined entry and exit points that are still obligatory to be inserted in a flight plan by the crews and to be flew over during the flight. The introduction of cross-border FRA is another milestone towards the improvement of flight and Air Traffic Management (ATM) systems efficiency. The purpose of the article is to examine the possibility of implementation and expansion of already existing cross-border FRAs and how much distance would be saved if it was possible to fly in a cross-border FRA, instead of a conventional FRA. Thus, two possible scenarios on the extract of a chosen flight route, based on a real-world flight, operated by inter alia LOT Polish Airlines, are examined. Route distance extension was calculated using the Horizontal Flight Efficiency method. Subsequent calculations include potential flight time savings along with fuel waste, CO2 emission and operating costs. The validation of the results obtained through calculation was conducted on X-Plane 11 as a simulation of two examined scenarios, using a Boeing 737-800. The results of the calculations and simulations indicate that the implementation and expansion of cross-border FRA may have a positive impact on flight efficiency improvement due to the reduction of distance and consequently the flight time, fuel waste, CO2 emission and operating costs. It can also mitigate the problem of the European Airspace capacity gradually reaching its maximum level. Thus, there is still a lot of place for further optimization of air traffic flow in European Airspace.

Influence of airspace avoidance due to political and safety issues on flight efficiency and environment

In the history of aviation there were many cases that led to the obligation or necessity to bypass certain airspaces, mainly due to political and safety reasons. One of the latest events is the incident over Belarusian airspace. The fundamental concept of the article is to examine the effects of the necessity to avoid certain airspaces by the operators, using the incident over Belarusian airspace as an example. Based on the observations of air traffic flow over affected region, route distance extension was calculated using the Horizontal Flight Efficiency method. Subsequent calculations include potential increase in flight time, fuel consumption, carbon dioxide emission and operating costs. The results were extrapolated to yearly amounts. based on the air traffic prediction reports. The air traffic prediction analysis as well as the results of the calculations and simulations indicate that the bypass of the airspaces on flight routes important to global economy, has a serious impact on the environment and operators’ budget due to increased aircraft’s fuel consumption resulting in growth of carbon dioxide emissions as well as operating costs. It also leads to deterioration in the European Airspace’s capacity, causing the necessity for Air Traffic Management units to reorganize the air traffic flow over the affected regions. Potential solutions mitigating the problem were also proposed.

The European airspace fragmentation: A cost-efficiency based assessment

The European airspace fragmentation: A cost-efficiency based assessment