Continuous climb and descent operations

Towards a flexible, optimum flight path that delivers major environmental and economic benefits.

Continuous Climb and Descent Operations (CCOs and CDOs) 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.

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 from top of descent and in a low drag configuration, prior to the final approach fix. Employment of these techniques reduces intermediate level-offs and results in time being spent at more fuel-efficient higher cruising levels, hence significantly reducing fuel burn and lowering emissions and fuel costs (see ICAO Doc 9993 and ICAO Doc 9931).

What can air travel industry do to reduce noise pollution?


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.

340,000 tons

tonnes fuel

1 mln +

tonnes CO2

150 million


1-5 dB


2018 ECAC-wide study

In 2018, EUROCONTROL conducted an ECAC-wide CCO and CDO analysis using 2017 traffic data, in order to estimate the potential network benefits of optimising the CCO and CDO in terms of fuel savings, emissions reduction and fuel costs.

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 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:

  • 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) *
  • The potential fuel saving benefits from CDO are in the region of x10 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.

European CCO/CDO task force

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 (VFE) performance in order to enable harmonisation at international level.

The task force has developed the CCO / CDO Tool Kit to support CCO / CDO implementation in Europe, consisting of the European CCO / CDO Action Plan, the CCO / CDO performance dashboard and the resources available on this webpage.

Following the TF#10 meeting in November 2020, the European CCO / CDO Task Force completed its mandate. CCO and CDO, together with VFE, are now a permanent agenda item of RNDSG (the Route Network Development Sub Group of NETOPS, the NETwork OPerationS Team).

RNDSG meetings take place 3x per year with a calendar of meetings and full meeting documentations available at OneSky Teams. For membership of RNDSG, please register to OneSky Teams and request to join the RNDSG Team.

At each RNDSG meeting, EUROCONTROL will report on current CCO / CDO performance and activities to work with stakeholders to optimise CCO, CDO and VFE across the network.

For any requests for support on CCO / CDO / VFE or any further information, feel free to contact us via the button at the bottom of the page.

Implementation support

At EUROCONTROL, we support the deployment of CCO/CDO. Our experts, in strong collaboration with stakeholders including air navigation service providers, aircraft manufacturers and aviation industry associations such as IATA, A4E, AIRE, EBAA, ERA, ACI and CANSO, measure and maximise the benefits achievable in the current ATM framework.

We look to support the aviation industry by making our wealth of knowledge and expertise available to the aviation industry in the form of our action plan, guides and list of reputable additional sources of information provided by stakeholders.

We also supports the creation of a more advanced CCO and CDO concept that will result from deploying future ATM tools and procedures. 

Action plan

We worked closely with our partners throughout the aviation industry to create a new action plan describing how potential constraints influence the ability to fly CCO / CDO together with key information on the mitigation proposals addressing these constraints in order to optimise the vertical flight efficiency of the climb and descent phases of flight.

Performance dashboard

The CCO/CDO performance dashboard measures:

  • Noise - for that part of the climb / descent profile where, according to SESAR, noise is considered the primary environmental impact;
  • Fuel - to measure the fuel burn / CO2 performance of the whole climb / descent profile, to Top of Climb (ToC) and from Top of Descent (ToD).

To our performance dashboard

Explore the CCO/CDO performance per state, airport and airline.

Watch our video to learn more about the harmonised European CCO / CDO definition, metrics and parameters for measurement.

We have gathered guidance material and supporting documentation to help our stakeholders' efforts to implement CCO/CDO and improve their operational efficiency. Below you will find a collection of documentation from across the industry. Some documents provided by our partners may require a subscription to access.

Do you wish to contribute your research paper?


Our EUROCONTROL Aviation Learning Centre provides a variety of CCO/CDO-related training courses and opportunities for career improvements. These include two related trainings:

  • an ATCO refresher training on CCO / CDO, which includes inputs from the Flight Crew side on what considerations have to be made within the aircraft to optimise the climb / descent profile; and,
  • a Flight Crew CBT on CCO / CDO, which includes inputs from the ATCO side on what factors must be taken into consideration to provide a safe and optimised descent profile to all arrivals.

Explore our latest courses on our Learning Zone - we have something for everyone.

Tailored support

At EUROCONTROL, we know that there is no one-size-fits-all solution. Thus, we take our implementation support one step further by providing our stakeholders with a direct line to our experts. If you have any questions, or need on-site support for your project, just reach out - we are here to help you optimise your efficiency.

Would you like our help?

Reach out and our experts will come back to you.