We are in the process of introducing a new electronic flight strip system called EXCDS in to our London Terminal Control Centre, which manages the airspace over London and the South East, some of the busiest and most complex airspace in the world.

With demand for our airspace growing, it is essential that we modernise the tools and technologies we use to manage airspace in order to increase capacity and ensure safety as traffic increases.

Further information about EXCDS and what we are doing to manage the transition in order to try and minimise disruption for our customers and their passengers can be found below.

What is EXCDS?

Blogs about EXCDS

Find out more about our transition to EXCDS in these posts published on our Corporate Blog.


What is EXCDS?

EXCDS is a new electronic flight strip system that we are currently introducing in to our London Terminal Control Centre, which manages flights entering and departing London and the South-East, some of the busiest and most complex airspace in the world. It will replace the existing paper strips system, which has served us well but will not cope with the demand that is forecast for the future. A flight strip is one of the core elements of an air traffic control system, providing an air traffic controller with all the relevant information about each individual aircraft, including its speed, altitude and destination.

Why are you introducing this new tool?

Our controllers currently use paper strips to manage air traffic within London Terminal Control. Whilst this has served us well, we need to move to an electronic system in order to meet future growth. EXCDS is part of a broader ten-year £1bn technology transformation programme at NATS, which will update many of the core systems used to manage air traffic in order to meet forecast growth, improve efficiency and  reduce our impact on the environment, whilst also maintaining and improving our already high safety levels.

What benefits will EXCDS deliver?

EXCDS offers two main benefits compared to paper strips. Firstly, it simplifies coordination between air traffic controllers, thereby reducing controller workload. Currently, Air Traffic Controllers have to call each other to pass aircraft between sectors. This is time consuming and adds to controller workload in what is already a complex operation. Introducing electronic coordination reduces the time spent on the phone, freeing up Controllers to manage the growing volumes of traffic being seen and laying the foundations for future growth.

Secondly, EXCDS introduces a conformance monitoring tool in to the London Terminal Control operation for the first time. This will automatically alert Controllers if an aircraft takes actions different to those instructed. This will enable the Controller to take remedial action swiftly and is expected to help reduce level-busts, whereby pilots mistakenly enter a different flight level to that which has been instructed.

Why will these changes cause flight delays?

The London Terminal Control operation is one of the most complex and busy airspace operations in the world. Transitioning our controllers on to new equipment in this operational environment requires very careful management. To help with the transition we will be limiting the volumes of traffic that enter the airspace they control for a short period during the initial stages of the transition.

For the first ten days there will be a 15% reduction in the maximum volume of traffic handled by those sectors, which will then reduce to 5% for the subsequent 10 days, though these rates may gradually increase during these phases as controllers gain confidence. Measures have been put in place to mitigate the impact, including for example by re-routing aircraft through other sectors. This has been planned in close cooperation with the airports and airlines most affected by this transition.

Why can’t you do this overnight when there are fewer flights?

Whilst the system itself will be implemented overnight, this is about providing our controllers with a new tool that they can use at all times to help manage growing traffic levels safely and efficiently. Our controllers have received significant training to prepare for the introduction of this tool. However, due to the scale and complexity of the London Terminal Control operation, it is necessary for us to reduce traffic levels slightly for a short period of time while our controllers get used to using the tool in that busy operational environment.

What airspace is covered by this transition?

This transition covers the airspace from North West London up to Birmingham, The airspace has a lot of climbing and descending air traffic, which means it is a busy sector. It also covers medium level airspace sectors that deal with traffic transiting traffic over London, for example travelling to and from Bristol and Cardiff airports and inbound to Luton and Stansted..

Am I likely to experience delay?

We do anticipate some delay during the initial phases of the implementation and we apologise to passengers for this. We have been working closely with the airports and airlines for over a year to put in place a comprehensive plan that will minimise the disruption caused by the transition. The introduction of EXCDS is an essential step in ensuring we can safely and efficiently manage future traffic demand and maintain the UK’s status as a global aviation hub.

How long is my flight likely to be delayed?

It is very difficult to accurately forecast in advance the levels of delay likely to be experienced by individual flights during this transition as this will be influenced by a variety of factors, some of which are out of our control, for example weather and the flow of traffic arriving through neighbouring ANSPs’ airspace. Many flights will experience no delay. Of those flights that do, most should experience only a short delay. However, there may be spells when the delay has a noticeable impact on passengers and for that we apologise. We have worked closely with airports and airlines ahead of the transition to minimise any disruption, and we will continue to do so throughout the transition period.

Why can you not be more specific about the anticipated delays?

There will be a large volume and flow of traffic through these sectors due to the combination of the summer schedule and the fact is that these are extremely busy sectors.  Throughout the transition we will be working closely with airlines and airports and we will continue to do everything we can to minimise delays.

Are any flights likely to be cancelled as a result of the disruption?

We do not anticipate any flights being cancelled as a result of the introduction of EXCDS. However, this would be a decision for individual airlines.

What have you done to mitigate potential disruption?

We are doing everything we can to minimise disruption to our customers and the flying public. The airports and airlines understand the importance of this change to the UK’s air traffic management infrastructure, and they have worked with us in advance of the transition to put in place the best possible plan to ensure the smoothest possible transition. Airlines and airports will also be present at our Swanwick Operations Centre during the transition so we can work together to put in place the right tactical measures during the initial days to minimise disruption.

Why do these changes have to be made now?

We are running out of airspace to cater for the UK’s future air travel needs. The tools and technologies we use to manage air traffic have a direct impact on the volume of traffic we can safely manage. While the tools and technologies in place today have served us well, we need new tools and technologies like EXCDS to help us manage future traffic growth.

What benefits will these changes bring in the long run?

We need to modernise our airspace and the tools and technologies we use to manage it in order to deliver the capacity required for the future and to maintain safety as traffic rises, while also reducing our impact on the environment.

Are these the only changes you’re making to ‘modernise’ the skies?

EXCDS is part of a wider £1bn technology transformation programme which will provide us with the tools and technologies required to meet growing demand for air travel, to ensure safety as traffic grows and to help reduce the environmental impact of the industry. 

Why does airspace need modernising now? (It’s been fine for all these years, why fix it if it’s not broken? etc)

We are running out of airspace to cater for the UK’s future air travel needs. Designed in the 1950s and 60s for aircraft that have long since retired, UK airspace handles traffic levels that have increased more than one hundred fold with traffic levels expected to increase by a further 40% by 2030. Imagine trying to put today’s road traffic through the road network of the 1960s. It would simply not work.

Neither is our airspace optimised either for communities close to airports or the global environment. We need to modernise our airspace to improve safety and deliver capacity, while reducing our impact on the environment. This will require close collaboration with our airport and airline industry partners, as well as the regulator and the Government to set out the case for change to secure buy-in from local communities.

Modernising our airspace will deliver many of the benefits airlines and local communities want to see – improved safety, increased capacity and efficiency.  Change is often difficult and we need to work closely with local communities to ensure we find solutions that strike the right balance between the needs of the country and our customers, and the impact felt on the ground.

EU law requires new navigational standards to be implemented by 2023; so doing nothing is not an option.  What we are trying to do is find the best way of implementing change, at the same time delivering significant environmental benefit and improving capacity to address future growth.

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