LORD adds speed and flexibility to decisions by Maastricht controllers


Maastricht Upper Area Control Centre (MUAC) began validating a new decision support tool in March. The Lateral Obstacle & Resolution Display (LORD) offers conflict resolution support for planning and tactical controllers, reducing cognitive load and adding a safety check for flight clearances.

Air traffic controllers at the EUROCONTROL Maastricht Upper Area Control Centre (MUAC) manage some of Europe’s busiest airspace, issuing clearances to up to 5,500 flights a day based on a deep understanding and knowledge of flight profiles. Software tools help to identify potential conflicts and bottlenecks, but they stop short of finding solutions or alternative trajectories, leaving all problem-solving to the controller.

A novel approach by MUAC’s systems development team – based on a concept originally devised by the Delft Ecological Design research group at TU Delft – combines controllers’ intuitive skills with a three-dimensional probe called the Lateral Obstacle & Resolution Display (LORD). LORD displays all possibilities and limitations of the current environment while allowing the controller to select the most appropriate clearance. The tool provides a concise overview of available and unavailable trajectories towards a probed flight level and presents this information to the controller in an intuitive and comprehensive graphical arc, representing the conflict and solution spaces. The tool can also be used to check or confirm a clearance and is configurable to suit individual controller preferences.

LORD scans each heading and flight level combination to identify limitations in the lateral and vertical dimensions, taking into account projected trajectories of the surrounding traffic. The tool also considers rate of climb, speed of turn and uncertainties such as pilot reaction time that accompany aircraft clearances. The controller can use the tool to probe different hypothetical manoeuvres or to check the availability of flight levels using the cleared flight level (CFL) menu populated by the ATC Real Ground-breaking Operational System (ARGOS). On opening the tool, conflicting trajectories are highlighted, and for each trajectory the projected conflict geometry and minimum distance between the aircraft pair are displayed. By simply moving the probe line, the controller can try out alternative routes towards any probed level.

“LORD displays constraints in the environment and presents alternatives for the controller to pick. It shows the information in a condensed form, cleverly combined to explain the options in an intuitive way to the controller.”

Marco Vismara System Development Operational Expert and Air Traffic Control Officer MUAC

Online validation

Online validation started in the MUAC Operations Room in March, where a dedicated group of controllers began testing the usability and accessibility of the tool, its display options and ease of use. About a dozen experienced controllers are complemented by a team of analysts, including human-machine-interface (HMI) and automation experts. Additional controllers will join the online validation group over the next few months to continue defining how the tool should operate based on their user experience and human factor principles. The aim is to introduce LORD to the entire Operations Room within a year.


“The solution is deeply embedded into the existing HMI so as not to put at risk functionality and workflow. We are leveraging HMI shortcuts to exploit more features and add to the capabilities of LORD.”

Sevastian Zakora HMI Software Engineer MUAC

In the initial version, the look-ahead time for LORD has been set to eight minutes. While there is no limit to the number of aircraft, only the conflicts with a projected minimum distance of not more than eight nautical miles are displayed, colour coded (orange or yellow) based on their severity. Similarly, the standard displayed arc presented to the controller currently extends 40 degrees on each side of the flight track, however it can extend up to 170 degrees each side when the route points for the subject flight justify such an expansion. Importantly, the tool does not prompt the controller to pick a specific solution or trajectory but displays all conflicts within the range and leaves the final decision to the controller.

“In line with the MUAC Automation Strategy and the Ecological Interface Design framework, we believe if a system only provides a single best trajectory in a complex traffic scenario, it will elicit either over- or under-reliance in the controllers (with associated human factors implications) instead of achieving the initial goal: optimised workload. Therefore, the system first needs to provide the context – an intuitive overview of all possibilities and limitations – in which the optimum trajectory can be embedded.”

Adam Tisza Automation, HF & UX Requirements Expert MUAC

In comparison with previous probing tools, the controller sees the availability of alternative trajectories at different flight levels. As a result, the controller benefits from reduced cognitive load and shorter input sequences for conflict avoidance or resolution. The controller still applies individual buffers; however workload is reduced, and the transparent nature of the tool means decision making becomes quicker and safer. The addition of further variables such as wind or environmental factors in the future is expected to bring even more insight to controller decisions.

LORD can be displayed in different ways, for example depending upon whether it is supporting the planner or executive controller. The click-and-hold trigger from any flight level suits tactical decision making where alternative trajectories can be seen at a glance. The planner, meanwhile, will benefit from the probe capability to assess different levels and/or trajectories before proposing a solution.

“The tool is so intuitive, it stays on screen for only a very short time, just for the decision. It displays all the information needed in a transparent and lean way to keep the controller’s focus on the real issues.”

Marco Vismara System Development Operational Expert and Air Traffic Control Officer MUAC

In-house development

LORD is the second decision-support tool displaying conflict and solution spaces based on Ecological Interface Design principles, introduced in the ARGOS server by MUAC’s systems development team. A menu shading function was added to the controllers’ display four years ago to indicate which flight levels are safe and which may lead to a conflict. This menu allows controllers to select and clear conflict-free flight levels via radio communication or datalink, uploaded directly to the aircraft’s cockpit. LORD takes this concept a step further by adding the lateral dimension on top of the vertical conflict scanning to generate a transparent conflict and solution space overview.

“These developments are part of our strategy to automate some of the less complex tactical traffic scenarios, and to provide advanced decision support for complex scenarios, in order to accelerate operator actions and thereby increase productivity. Our objective is to continuously improve our operational performance to accommodate future traffic demand."

John Santurbano Director MUAC
Adam Tisza, Marco Vismara, Sevastian Zakora & Humberto Carvalho

The ARGOS server performs computations based on flight data and surveillance data to identify optimal trajectories and solutions that support safe and efficient operations using a deterministic model that emulates strategies used by controllers. While certain components of the deterministic resolution could make use of a machine-learned (ML) model in the data analysis phases, such as the calculation of variable speed and/or climb/descent rate in the trajectories, neither artificial intelligence (AI) or ML models are used in the tactical decision and execution phases of separation assurance. This is due to the lack of explainability of AI in a system that interacts and collaborates with controllers.

“ARGOS processes trajectories with fine-grained accuracy and precision. A wide range of manoeuvres, uncertainty and complex separation rules are carefully considered. State-of-the-art algorithms and immense computing power are required to achieve real-time processing in MUAC’s dense airspace.”

Humberto Carvalho Software Engineer MUAC

The systems development team deployed a web-based prototype to speed up the development process that enabled software engineers and HMI experts to work in parallel. Using past traffic data to feed the algorithms, prototyping and testing took place at the same time over a condensed time period between 2020-2023. Air traffic controllers are greatly involved and provide crucial operational knowledge. It is an iterative process that aims to converge towards next-generation ATM tools that provide high operational value

Future steps

MUAC has an ambitious vision to revolutionise air traffic control and manage its airspace more efficiently under the banner of ARGOS. In addition to providing high-level decision support for controllers handling complex and challenging scenarios, routine traffic and actions should benefit from highly automated support tools. The development team is working on an algorithm to determine if a flight is involved in a complex scenario, or whether it can be handled by automation under the supervision of the planner in a datalink environment. This leaves the executive controller free to focus on core issues while an automated “second executive” handles simple scenarios. The planner retains an overview of the entire sector which is managed by two agents.

Working in partnership with the German Aerospace Centre (DLR), MUAC is developing operational procedures aimed at contrail prevention, for example avoiding ice-super-saturated regions using modified trajectories. With more than half of the impact of aviation on climate change believed to come from aircraft non-carbon emissions, preventing contrails is rapidly growing in importance. ARGOS is set to help automate and integrate these calculations into the operational environment, combined with development of human factor elements and optimum trajectory calculations using iterative prototyping methodology.

Introducing new concepts relies on an expert team that crosses multiple domains including HMI and software analysts, air traffic controllers and human factors experts. MUAC draws on all these capabilities to ensure the focus remains on delivering safe and expeditious air traffic management.


In order to let EWG4KA descend to its Transfer Flight Level (250), the ATCO might feel inclined to let it turn right and pass behind CAO1031. LORD raises awareness that CAO1031 is flying in conformance with its route, including an imminent turn, which will not allow for such a solution. Furthermore, a right turn would bring EWG4KA into another conflict down the sector with EZY13AP, which is also about to descend to flight level 250. At a glance, LORD indicates that both conflicts can be avoided by a slight left turn, granting all three flights unrestricted, continuous descents.

Image behind the title: LORD tells the ATCO ROT361C may be descended to its Transfer Flight Level (260) if adhering to its present track.

“We have a very agile team that is able to prototype new concepts very efficiently and quickly. This still requires a huge amount of software development, but the process takes weeks rather than months and requires significantly fewer resources. Such an approach allows the users to evaluate crude prototypes very early on and see their feedback being implemented at a fast pace.”

Adam Tisza Automation, HF & UX Requirements Expert MUAC

Get our latest issue of Skyway

Explore our latest articles and download the full issues.

Latest highlights

Press release

EUROCONTROL calling for common action to address air traffic control delays

EURO 2024 - banner

Coordinating to ensure efficient air traffic during EURO 2024!

All together now 2024

All Together Now 2024 video: Why mitigating bad weather impacts on aviation is a top priority this summer

All together now 2024

All Together Now 2024 video: Why realistic scheduling is vital to a well-functioning network

Press release

EASA & EUROCONTROL sign MoC to enhance cooperation for the safe and sustainable future of European aviation

All together now 2024

Preparing together for busy summer traffic 2024: EUROCONTROL and European aviation executives meet in Brussels