NATS is working with the military, airlines, flight planning service providers, and other air navigation service providers to increase the number of flights making use of Conditional Routes, known as CDRs.

Currently some 75% of flights that use CDRs actually plan to do so, as they provide more direct routes which reduce track miles and flying time, saving fuel and money. However, there is still potential to increase the use of them further, by speeding the flow of information to airline operators so that they can make the most of available opportunities.

What are CDRs and how often are they available?

Conditional routes typically go through areas of airspace which are used by the military for their operations. When the military isn’t using them, they are available for use by non-military aircraft. By their nature, therefore, CDRs are not available all of the time.

In simple terms, Military Airspace Planners agree the hours of operation with the State and civil planners, and thus the availability of the conditional routes.

While air traffic control may be able to offer airlines better tactical routings through these areas, there are even more benefits if airlines are able to flight plan to use these routes, because it means they can plan to carry less fuel which in itself is a saving.

The infographic below shows how the availability of military airspace and CDRs are considered at all stages throughout the flight planning process and during flight itself. NATS is also developing post flight analysis to help airlines determine where there may be opportunities to benefit from using these routes.

I was talking to Chris Woodland, Air Traffic Services Manager at Thomas Cook about CDRs and this is what he told me:

“We already aim to make the most of available CDRs – they are not only good for our customers, helping us to fly more directly and therefore reducing our flight times and cost, but also benefit the environment as we burn less fuel and therefore we are able to reduce our overall emissions for the flight. We will be looking to continue to optimise our flight plans through utilising CDRs whenever they are made available and in the future under a dynamic hand back process be able to re calculate flights to further improve our efficiencies.”


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Michael Lyddon

Great to see the Flexible Use of Airspace concept as the focus of a post. As a former Officer Commanding Military Airspace Booking and Coordination Cell based within the UK AMC, the joint effort of RAF and NATS personnel in making the airspace more efficient for all users is commendable. Much is also being done to educate Military Airspace Users to make more intelligent use of the airspace, booking only what is absolutely necessary, and releasing airspace back in order to activate CDRs at the earliest opportunity.


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