Continuous Climb and Descent Operations

Continuous Climb and Descent Operations (CCO and CDO) are aircraft operating techniques enabled by airspace design, instrument procedure design and facilitated by Air Traffic Control (ATC). 
CCO and CDO allow aircraft to follow a flexible, optimum flight path that delivers major environmental and economic benefits - reduced fuel burn, gaseous emissions, noise and fuel costs - without any adverse effect on safety (see ICAO Doc 9993 and ICAO Doc 9931).
CCO and CDO operations allow arriving or departing aircraft to descend or climb continuously, to the greatest extent possible. Aircraft applying CCO employ optimum climb engine thrust and climb speeds until reaching their cruising levels. With CDO, aircraft employ minimum engine thrust, ideally in a low drag configuration, prior to the final approach fix. These techniques result in more time being spent at more fuel-efficient higher cruising levels, hence significantly reducing fuel burn and lowering emissions and fuel costs.


Deployment of optimised CCO and CDO throughout Europe will be beneficial to all European ATM system stakeholders and will help the network to address the environmental challenges it faces.
The results of EUROCONTROL studies (scroll down for more information) have shown that on average the benefit of optimising CCO/CDO would result in fuel savings of up to 350,000 tonnes of fuel (1m tonnes+ CO2) or 150+ million €. In addition, using CDO can reduce noise by 1-5dB compared to a non-CDO operation. (Source: European Joint Industry CDA Action Plan).

Implementation Support

EUROCONTROL supports CCO and CDO deployment. A dedicated team works with stakeholders (ANSPs, aircraft manufacturers and aviation industry associations such as IATA, ERA, ACI and CANSO) to measure and maximise the benefits achievable in the current ATM framework. The team also supports the facilitation of a more advanced CCO and CDO concept that will result from deploying future ATM tools and procedures. A guide to implementing Continuous Descent is available. 

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The European CCO and CDO Task Force

Historically in Europe, the implementation of CCO and CDO operations has been encouraged on an ‘as-much-as-you-can’ basis while, until recently, there has been no harmonised definition of what actually constitutes a CCO or CDO operation. 
In addition, there has been no assessment of the potential network-wide benefits that could be realised by optimal CCO and CDO operations.
In 2015, a task force of European ATM stakeholders was created with the objective of agreeing harmonised definitions, metrics and parameters to measure CCO and CDO operations in Europe. The resulting harmonised definitions, metrics and parameters agreed by the Task Force are recommended to be used by any European ATM stakeholder for the measurement of CCO, CDO or vertical flight efficiency performance in order to enable harmonisation at international level.
In 2018, EUROCONTROL conducted an ECAC-wide CCO and CDO analysis using 2017 traffic data, based on the outcomes of the Task Force in order to estimate the potential network benefits of optimising the CCO and CDO in terms of fuel savings, emissions reduction and fuel costs.

Results of the study

For CCO, the study concluded that 94% of flights in ECAC currently fly CCO to FL (Flight Level) 100 while 74% fly a full CCO to Top of Climb (ToC).
For those flights currently flying non-CCO profiles, the average time in level flight to the ToC was 168 seconds with per-flight savings estimated at 15kg fuel/48kg CO2/7EUR. Across the network this would result in a potential average per-departure saving of 4.3kg fuel/13.7kg CO2/~2€
For CDO, the study concluded that whilst 41% of flights fly CDO from FL75 (the top of the noise CDO) while only 24% fly a CDO from Top of Descent (ToD – the top of the fuel CDO). 
For those flights currently flying non-CDO profiles, the average time in level flight from the ToD was 217 seconds with per-flight savings estimated at 46kg fuel/145kg CO2/20EUR. Across the network this would result in a potential average per-arrival saving of 35kg fuel/110kg CO2/15€.
The ECAC-wide study identified two main conclusions:

1) The results indicate that in Europe the potential savings from optimising CCO and CDO are up to 340,000 tonnes fuel/year, (1.1M tonnes CO2/150M EUR) *; and,
2) The potential fuel saving benefits from CDO are in the region of x10 of those from CCO.
* It should be noted that the achievement of 100% CCO and CDO across the European network may not be possible for a number of reasons, such as safety (i.e. the need to keep aircraft separated by a certain distance or time), weather, capacity or ATCO workload, all of which may be considered as interdependencies, while small inefficiencies in the system are required to operate a flexible and operationally efficient network.

The results of the ECAC-wide study show that the potential benefits available to operational stakeholders are huge and therefore, in early 2018, the CCO/CDO Task Force was reactivated with the objective of identifying the following:

  • What are the barriers to more CCO/CDO being flown?
  • Which barriers can the CCO CDO Task Force address to achieve more CCO/CDO?
  • What can ATM stakeholders do to promote more CCO/CDO?

The work of the Task Force is ongoing and is expected to be completed by 2019 with the delivery of an updated CDO Action Plan document and a “State of Play’ document on CCO/CDO.

More information will be detailed on the website once it becomes available.

Update 21st June 2018

As a result of the latest Task Force discussions, one of the parameters for measuring CDO has been updated. The CCO / CDO Task Force now recommends that a single level segment of up to 30 seconds, if undertaken at a level immediately prior to glide slope intersection, be allowed in the measurement of CDO and therefore the time taken for such an event will not be treated as inefficiency. For example, when a level segment of 45 seconds is flown prior to glide slope interception, only 15 seconds of a level segment will be recorded. This single 30-second event provides a realistic buffer for glide slope interception based on ‘distance-to-go’ accuracy, pilot technique and experience, non-constant wind values at different altitudes and some FMS capabilities.

The harmonised definitions, metrics and parameters for measuring CCO and CDO have been agreed between the members of the European CCO/CDO Task Force. The outcomes of the Task Force will remain stable unless detailed operational evidence is generated which suggests that the parameters for measurement of CCO/CDO on a harmonised pan-European level may be further optimised.

Watch the video below to learn more about the definitions, metrics and parameters proposed to measure CCO and CDO.


Continuous Climb and Descent Operations (CCO/CDO)

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