eATM Portal

ENV01 — Continuous Descent Operations (CDO)

A continuous descent operation (CDO) (1) is an aircraft operating technique, enabled by airspace design, procedure design and ATC clearances in which arriving aircraft descend without interruption, to the greatest possible extent, by employing minimum thrust in order to optimise the descent profile in terms of fuel burn. The optimum vertical profile takes the form of a continuously descending path.

Operating at optimum flight levels is a key driver to improving fuel efficiency and minimise carbon emissions as a large proportion of fuel burn occurs during the climb phase.

Many major airports now employ PBN procedures which can enable both CDO and continuous climb operations (CCO) and, in a large number of cases, judicious airspace and procedure design has resulted in significant reductions in environmental impacts. This is particularly the case where the airspace design has supported CCO and CDO.

CDO does not adversely affect safety and capacity and will produce environmental and operational benefits including reductions to fuel burn, gaseous emissions and noise impact.

It is important that monitoring and measuring of CDO execution is defined across ECAC using harmonised definitions to avoid misleading interpretations of performance measurement. It is equally important that CDO execution is measured across ECAC, as far as practicable, using a harmonised methodology and parameters. Whilst reporting can be undertaken at the local level according to local legislation and requirements, when CDO execution is reported on an international basis, this measurement should always be based upon a harmonised method, parameters and metric. The proposed methodology (4) identified by the European TF on CCO/CDO is detailed at

(1) Since the publication of ICAO Doc 9931, the term Continuous Descent Operations (CDO) has generally replaced the term CDA (Continuous Descent Approach).
(2) In principle, it is not required to implement CDO on a 24/7 basis, but it should be facilitated to the extent possible, according to local conditions.
(3) The methodology is detailed in the European CCO / CDO Action Plan, see

NOTE FOR MILITARY AUTHORITIES: It is the responsibility of each military authority to review this Objective IN ITS ENTIRETY and address each of the SLoAs that the military authority considers RELEVANT for itself. This has to be done on top and above of the review of "MIL" SLoAs which identify actions EXCLUSIVE to military authorities.

Air Navigation Service Provider / Airport Operator / Airspace Users


Related Elements

Applicability Area(s) and Timescales

Applicability Area:
See list of airports in MP Level 3 Implementation Plan - Annexes
Timescales From By Applicable to
Initial operational capability 01-07-2007 Applicability Area
Full operational capability 31-12-2023 Applicability Area

Links to SESAR Solutions

Links to PCP ATM Sub-Functionalities


Applicable legislation
Regulation (EU) 598/2014 of 16 April 2014 on the establishment of rules and procedures with regard to the introduction of noise-related operating restrictions at Union airports within a Balanced Approach and repealing Directive 2002/30/EC (as from 16/06/2016).
EC Directive 2002/49/EC, dated 25.06.2002 relating to the assessment and management of environmental noise.
EC Directive 2008/50/EC, dated 21.05.2008 on ambient air quality and cleaner air for Europe.
Applicable ICAO Annexes and other references
ICAO Annex 16 - Volume I - Aircraft Noise
Deployment Programme 2022
Operating Environments
Terminal Airspace

Expected Performance Benefits

Operational efficiency
CDOs contribute to reducing airlines operating costs including a reduction in fuel consumption by the flying of optimised profiles (no vertical containment required). If the CDO is flown as part of a PBN procedure, the predictability of the vertical profile will be enhanced for ATC.
CDOs are also a proxy for Vertical Flight Efficiency (VFE) and should be monitored according to harmonised definitions and parameters in order to measure efficiency.
Cost efficiency
Reduction of fuel burn (and consequently, atmospheric emissions) has been estimated to be 51kg per flight for those flying CDO over those flying non-CDO. In addition, studies have indicated that due to lower drag and thrust facilitated by CDO, over certain portions of the arrival profile, noise can be reduced by up to 5dB.
  Code Title From By Related Enablers
ASP01 Implement rules and procedures for the application of CDO techniques
  • 01-07-2007
  • 31-12-2023
ASP02 Design and implement CDO procedures enabled by PBN
  • 01-01-2018
  • 31-12-2023
ASP03 Train controllers in the application of CDO techniques whenever practicable
  • 01-07-2007
  • 31-12-2023
ASP04 Monitor and measure the execution of CDO
  • 23-03-2018
  • 31-12-2023
APO01 Monitor and measure the execution of CDO
  • 01-01-2018
  • 31-12-2023
USE01 Include CDO techniques in the aircrew training manual and support its implementation wherever possible
  • 01-07-2007
  • 31-12-2023
Code Dates
1999 99
2000 00
2001 01
2002 02
2003 03
2004 04
2005 05
2006 06
2007 07
2008 08
2009 09
2010 10
2011 11
2012 12
2013 13
2014 14
2015 15
2016 16
2017 17
2018 18
2019 19
2020 20
2021 21
2022 22
2023 23
2024 24
2025 25

Supporting Material

Title Related SLoAs

EUROCONTROL - CCO / CDO Performance dashboard

APO01, ASP01, ASP03, ASP04, USE01

EUROCONTROL - CCO, CDO harmonised definitions, metrics and parameters

APO01, ASP04, USE01

EUROCONTROL - CDO refresher course for ATCs

APO01, ASP03, ASP04, USE01


APO01, ASP01, ASP02, ASP03, ASP04, USE01

EUROCONTROL - European CCO/CDO Action Plan

APO01, ASP01, ASP02, ASP03, ASP04, USE01

EUROCONTROL - IANS-ENV-INTRO - Introduction to Environment -e-learning training course 12/2012

ASP03, USE01

ICAO - Doc 4444 - Air Traffic Management - Edition 16 / 11/2016

ASP01, ASP02

ICAO - Doc 9426 - Air Traffic Services Planning Manual - Edition 1 / 12/1992

ASP01, ASP02

ICAO - Doc 9613 - Performance-based Navigation (PBN) Manual - Edition 4 / 03/2013

ASP01, ASP02

ICAO - Doc 9931 - Continuous Descent Operations (CDO) Manual - Edition 1 / 12/2010

ASP01, ASP02, ASP03, USE01

Consultation & Approval

Working Arrangement in charge
Airport Operations Team (AOT)
Outline description approved in
Latest objective review at expert level
Commitment Decision Body
Provisional Council (PC)
Objective approved/endorsed in
Latest change to objective approved/endorsed in