Continuous climb and descent operations

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

Status of Task Force work flows following the TF#4 meeting (March 2019)

CCO / CDO Action Plan update – The update to the CCO / CDO Action is on track. Several sets of comments have been received. A proposal for a document structure with an executive summary followed by the actions / supporting information with the SoP document incorporated as a supporting annexe was received. A proposal was also made to have a checklist of actions for stakeholders to demonstrate their implementation of the actions. Content will be reviewed again with mature content and structure to be proposed by TF#5 meeting (17-18 June 2019).

CCO / CDO state of play (SoP) document – The SoP document has undergone a detailed review since TF#3 and contains much new content. Additional sections will be updated prior to TF#5 with volunteers for sections missing content to be identified and proposed. The structure in terms of content is agreed. Additional use cases for any CCO / CDO best practices are requested with examples sought from all geographical areas of Europe to demonstrate widespread applicability of best practices and not focusing on a few specific examples. Mature content and structure will be proposed at TF#5 meeting.

AIP CDO best practice analysis – The AIPs for 100 European airports have been reviewed. CDO content varies from very good practice to bad practice to nothing. Harmonised text proposals will be made based on current AIP best practice text for a general section for the AIP (ENR3.3) and a set of generic texts for the AD section (on sections such as phraseology, DTG provision, charting etc.) Input is being requested from companies such as Jeppesen, Sabre, Lido and NAVBLUE on how they transpose AIP information into the Operating Manuals of airlines in order to ensure the harmonised texts are proposed for the correct sections.

CCO / CDO performance tables – The proposed performance tables for monthly performance figures on CCO / CDO based on the harmonised European TF-agreed definitions, metrics and parameters for measurement, are gathering a lot of attention. They will be developed for all airports in Europe and all airlines flying in Europe and enable comparisons between individual performance and the average performance at each airport. The basic functionality would be monthly CDO figures (average time in level flight) from top of descent for the airport / airline selected. Enhanced functionality would include slicing / aggregation by a/c type, country, alliance, type of flight, CCO / CDO, level band, time of analysis, FAB etc. with vibrant charting possibilities. A test data set should be shared by TF#5 with the basic functionality to be available before the end of 2019. Based on the experiences of stakeholders who use similar performance tables, we expect that airlines will gain significant fuel saving benefits with performance comparisons generating interest in any optimised procedures of the best performing airlines.

Airline CDO questionnaire – The airline CCO / CDO best practice questionnaire was sent out in collaboration with the stakeholder organisations. It contained 10 questions on airline CDO SOPs, airline guidance to pilots on CDO, CCO / CDO pilot training material, airline best practices on CDO training, CDO performance measurement, pilot feedback on CDO performance, airline targets on CCO / CDO and airline impressions of how more CDO could be enabled. The questionnaire has so far received over 100 responses from over 40 airlines. The co-chairs are following up with individual contacts to ensure that all major European airlines are represented with responses. The results of the questionnaire will be fed back to TF#5 and to the stakeholders' organisation representatives on a one to one basis. The outcomes will feed TF proposals for best practice material on CCO / CDO for the airlines.

ATCO refresher training – Proposals for updates to the ATCO Common Core Content (CCC) have been made including mandatory content on CCO, a specific CCO/CDO Objective with higher taxonomy level to indicate more simulation exercises and a new objective on ATCO training on aircraft energy management. IANS will create a refresher training on aircraft energy management in collaboration with the TF based upon content already provided by TF members. A small TF sub-group will agree on the content for the refresher training. IANS will then take the content and ‘convert’ it into an eLearning course structure by identifying the best way to convey the various messages in a pedagogically sensible way. The tentative aim of IANS is to complete this refresher training by the end of summer.

ERNIP update – The TF is proposing textual updates to the ERNIP (European Route Network Improvement Plan) document with the aim to ensure that CCO/CDO are integrated into the airspace design process, the main principles of airspace design relating to CCO/CDO are detailed and there is a link to the relevant sources that can help airspace designers from the CCO/CDO point of view. Several sets of comments for proposals were received from TF members. The proposals will reinforce the message that CDO should be optimised from ToD / higher levels where possible, together with the requirement to regularly review LoAs and proposals to consider flexible LoAs. Any changes to the ERNIP document need to be approved by the NM Board, therefore, all proposals will be delivered by the TF to RNDSG/98 (September) in order to get approval at the NM Board meeting (December 2019).

Airspace change collaboration – At RNDSG/96, the CCO / CDO TF proposed to collaborate with stakeholders on identifying suitable airspace change proposals where advanced CDO-enabling concepts could be incorporated into the airspace design process and where stakeholders could work together with the CCO / CDO TF to develop some fully optimized CDO airspace proposals. Collaboration has been preliminary agreed with Madrid and the TF is currently waiting to review their proposals for the airspace change.

CDO performance data availability – The TF is maintaining collaboration with OpenAirlines and StorkJet, companies that specialise in aircraft performance monitoring by using big data analysis techniques on QAR / FDR (Quick Access Recorder / Flight Data Recorder) data. Aircraft fuel burn data is the optimum source of CDO performance measurement data and the first measurements seem to be promising, however, based upon the limited amount of data that such companies are currently processing and the lack of the compulsory provision of fuel burn data by airlines, such data is not currently a viable source for CDO performance measurement at the European scale. The TF needs to maintain collaboration with such companies and actively seek participation or information from other organisations that undertake big data analyses using QAR / FDR data e.g. Aviaso (Honeywell) and Boeing.

Trajectory downlink data - The SPI-IR (Surveillance, Performance and Interoperability - Implementing Rule 1207/2011 and subsequent amendments) mandates parameters for downlink by Mode S. There is a complicated process to include new parameters to be downlinked that includes ICAO Panel engagement, discussions with the manufacturers on whether there is a link in the cockpit between the desired parameters and the transponder, and discussions with the SMOs (Standard Making Organisations e.g. EUROCAE / RTCA) on potentially updating the transponder MOPS (Minimum Operational Performance Specifications). In addition, Airbus provided input that they are not planning to implement new functionalities that can be shared via ADS-B such as future FMS prediction and that in SESAR, there is a clear strategy of promoting the sharing of 4D trajectory information via ADS-C as a key enabler. The TF needs to follow up with the relevant experts to ensure the continuation of the discussion on the possibilities of the downlinking of current data (ADS-B) and predictive data (ADS-C).

CCO / CDO TF meeting #5 - The next meeting will take place on the 17-18 June 2019 at EUROCONTROL. At the next meeting, mature versions of the TF key deliverables (CCO / CDO Action Plan and SoP document) will be reviewed, an update will be provided on all ongoing workflows together with specific detailed updates on ATCO refresher training, the outcomes of the airline questionnaire and proposals for the content of harmonised AIP best practice material. In addition, inputs (presentations and information sharing) have been requested from the relevant experts on current and emerging issues such as new CDO performance measurement data sources (QAR / FDR data), trajectory intent discussions, transposition of AIP data to airline manuals and CCO / CDO performance information from specific projects.

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).

340,000 tonnes

fuel savings (1 million+ tonnes CO2)

150 +


1-5 dB

noise reduction

Implementation support

We, at EUROCONTROL, support CCO and CDO deployment. A dedicated team works with stakeholders (ANSPs, aircraft manufacturers and aviation industry associations such as IATA, A4E, AIRE, EBAA, 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. 


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.

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.

What are Continuous Climb and Descent Operations (CCO and CDO)?

What can air travel industry do to reduce noise pollution?

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.

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.