When it comes to air traffic control (ATC), our top priority is ensuring the safety of the skies. To achieve this, we sometimes need to implement what are called Air Traffic Flow and Capacity Management (ATFCM) measures. Essentially, these measures allow us to manage demand in different parts of the airspace so that traffic levels always remain safe.

These “flow” measures, as they are sometimes known, consider factors that can have an impact on airspace capacity and intervene on a flight-by-flight basis to moderate the traffic flying on a particular route, or through a particular piece of airspace. There are different types of measures that we can apply. Some reroute traffic either laterally or vertically whilst others reduce the number of aircraft flying on a route (or through a piece of airspace) at any one time in order to keep the airspace safely managed. In order to achieve the reduction in the number of flights and to spread the demand efficiently, aircraft are issued with Calculated Take Off Times (CTOTs) or “Slots” as they are better known. These slots allow an aircraft a 15 minute window within which it needs to depart, or otherwise request a new “slot”.

We exist to make the skies an even safer and more efficient environment for aviation.

Flow measures are essential in scenarios such as adverse weather conditions, military activity, and excessive aircraft demand on specific routes. Storms, for example, can be incredibly difficult to pinpoint when it comes to times and location, causing further complications and may require flow measures to be put in place to help minimise controller workload and traffic complexity. While safety remains our primary focus, we make every effort to minimise the impact on aircraft when these measures are put into action so that unexpected delays are prevented as much as possible. Even when we reduce the number of aircraft in a specific airspace, we work diligently to optimise its use and minimise disruptions.

Our Network Operations Teams within the Flow Management Position (FMP), based at both Swanwick and Prestwick, is in constant collaboration with airlines, our on-site UK Met Office forecasters, airports, the military and other key stakeholders. This collaborative teamwork helps us reduce the likelihood of last-minute measures and allows us to plan effectively. Additionally, we maintain a close relationship with European Air Navigation Service Providers to optimise European routes. The application of “Slots” is managed through Eurocontrol in their role as the overall European “Network Manager”

While sometimes regulations have to be implemented on the day, we also plan for known events well in advance – often up to two years ahead. This extended planning period allows us to refine our strategies as the date approaches and factor in immediate capacity considerations from five to one day before implementation. This forward-thinking approach enables us to prepare for large events, seasonal traffic, and other known components that could constrain airspace capacity. For example, despite the dreary autumn weather, our team are currently planning for the busy summer holidays for 2024, factoring in trending locations that could lead to a higher aircraft demand on particular air traffic routes, as well as weather trends and possible geopolitical factors. By planning ahead, delays can also be minimised and reduce unexpected air holding. This helps to minimise the environmental impacts.

After we implement flow measures, we conduct a thorough post-operation analysis. This step helps us learn from each experience, identify any lessons, and improve our approach for the future. We regularly engage with airlines to discuss the measures we have implemented, allowing us to fine-tune our strategy and enhance our performance. It is through this collaborative effort, continuous reflection, and years of experience that we have earned our reputation as a world leader in air traffic management.

Your safety in the skies is our utmost priority, and we are dedicated to making your journey as smooth and secure as possible.


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