Operational Interdependencies

 The importance of taking interdependencies into consideration

Decisions relating to operational changes are often made on the basis of a wide range of strategic, economic, operational and impact-related information.

Often a compromise or balance is required to ensure that a disbenefit, or a combination of disbenefits, does not outweigh the value of the anticipated benefits. Thus when performing an environmental assessment and using the results to inform decision making, it is important to consider interdependencies or trade-offs of the proposed action and/or alternatives, to avoid, where possible, any unintended consequences.

Definitions of interdependency and trade-off

It should be noted that, in the context of this website, the term “interdependency” is used to refer to a situation where a change in Factor A results in a change to Factor B (and vice versa), whereas the term “trade-off” is used to describe interdependency where an improvement in Factor A results in a detrimental change to Factor B.

Note: As the initial paragraph for each reference document was taken directly from the ICAO Publications Catalogue, it includes references to airlines, air carriers, aircraft operators, etc. These should be read as referring to all operators of aircraft, and not to any specific group.

The following pages contain a set of annotated bibliographies of ICAO documents that contain relevant information on interdependencies, and are laid out in the following standard format:

  1. ICAO Document number – URL (with Title), Publication date, Edition, ISBN number.
  2. Brief description of the document (from the ICAO publications catalogue)
    Details of the Chapter or Section containing the information including a tag noting environmental, or environmental plus non-environmental interdependencies information. This is then followed by a brief top-level description of the major content of the chapter or section, and which environmental impacts are identified.
  3. Connections to other ICAO documents.


List of Keywords
Operational Opportunities to Reduce Fuel Burn and Emissions (Doc 10013)Emissions, Fuel
Doc 10013 | 2014 | First edition | ISBN - 978-92-9249-412-4

This document identifies and reviews various operational opportunities and techniques for minimizing fuel consumption and therefore emissions in civil aviation flight and ground operations. It should be noted that the circular is not intended to be the basis for regulatory action but examines some of the primary considerations associated with operational opportunities and the benefits and technical limitations that may be associated with them.

The document provides some general high level information on the operations techniques for minimizing aircraft fuel consumption. It also states the operational restrictions that may need to be considered including safety, legal constraints and environmental trade-offs, and contains a number of references to both environmental plus non-environmental interdependencies.
It provides information about the potential trade-off between reducing aircraft noise and reducing engine emissions and states that most techniques used to reduce the impact of aircraft noise near airports tend to increase fuel consumption, having a negative effect on the environment.

This document identifies operational opportunities to minimize fuel use and to reduce emsission in the following areas:

- Airport operations
- Maintenance
- Weight Reduction
- The effect of payload on fuel efficiency
- Air traffic management
- Flight/route planning and other operational issues
- Aircraft operations
The document also mentions the ICAO standards for aircraft engine certifications and states that new CO2 standard development is complex and lengthy due to the trade-offs that exist between CO2 and NOx. In the “Trends” section it states that new technologies are being investigated and provides the example of engines operating at higher combustion temperatures, which can reduce fuel burn and CO2 but also tends to increase NOx emissions.
Links to information contained in:
•ICAO Doc 9814 – Airport Planning Manual, Part 2, Land Use and Environmental Control, Chapter 5 — Land-use Planning.
•ICAO Doc 9888 – Noise Abatement Procedures: Review of Research, Development and Implementation Projects - Discussion of Survey Results
•ICAO Doc 9931 – Continuous Descent Operations (CDO) Manual
Performance-based Navigation (PBN) Manual (Doc 9613)Interdependency / Interdependencies
Doc 9613 | 2013 | Fourth edition | ISBN 978-92-9249-175-8

​This manual aims to provide guidance to States, ANSPs and airspace users on how to implement RNAV and RNP applications. The purpose of this manual is to provide guidance in identifying whether, by a suitable adjustment of the airspace concept, navigation application and / or infrastructure, it is possible to make use of an existing navigation specification, thereby obviating the need for a specific and potentially costly imposition of a new certification requirement for operation in an individual airspace.

Part B (implementation guidance) of this manual includes references to trade-offs and chapters 2.2 and 2.3 of this manual contain information about operational environmental plus non-environmental interdependencies relating to implementing competing key performance areas (KPA). It refers specifically to the trade-offs between KPAs required for the placement of Terminal Control Area (TMA) arrival and departure routes ( and how traffic sample assumptions for simulating new operational concepts should be undertaken bearing in mind the competing KPAs.

Links to information contained in:

•ICAO Doc 4444 – Procedures for Air Navigation Services — Air Traffic Management (PANS-ATM)•ICAO Doc 8168 – Procedures for Air Navigation Services — Aircraft Operations, Volumes I and II (PANS-OPS)
•ICAO Doc 9426 – Air Traffic Services Planning Manual
•ICAO Doc 9992 – Manual on the Use of Performance-Based Navigation (PBN) in Airspace Design
•ICAO Doc 9905 – Required Navigation Performance Authorization Required (RNP AR) Procedure Design Manual
•ICAO Doc 9992 – Manual on the Use of Performance-Based Navigation (PBN) in Airspace Design •ICAO Doc 9906 – Quality Assurance Manual for Flight Procedure Design, Volume 5 — Validation of Instrument Flight Procedures.
Noise Abatement Procedures: Review of Research, Development and Implementation Projects – Discussion of Survey Results (Doc 9888)Interrelationship / Interrelationships, Trade-off / Trade-offs, Noise
Doc 9888 | 2010 | First edition | ISBN 978-92-9231-665-5

This document summarizes Noise Abatement Procedure (NAP) Research and Development (R&D) projects undertaken by various parties, including universities, regulatory agencies, manufacturers, air carriers and airports. The summaries are a result of survey questionnaires that were distributed to contact persons for NAP R&D in 2005–2006 and to CAEP Member States and observers in 2008.

In the overview section of the document, the authors recognize that in general, Continuous Descent Operations (CDO) procedures appear to provide both noise and emissions benefits, however other noise abatement procedures have the potential to, or do in fact, increase emissions.  The document included a review of NAP R&D projects prepared for CAEP/8 and noted that the research compendium did not include an assessment of trade-offs against fuel burn, emissions, flight time and capacity.  The document includes an Appendix C, which presents the survey results for NAP R&D projects.  Each of these survey responses includes a discussion of whether and how a project addressed environmental interdependencies and trade-offs.

Links to information contained in:

•ICAO Doc 8168 Volume 1 – Procedures for Air Navigation Services – Aircraft Operations (PANS-OPS)
Effects of PANS-OPS Noise Abatement Departure Procedures on Noise and Gaseous Emissions (Circular 317)Noise, Emissions
Circ 317 | 2008 | First edition | ISBN 978-92-9231-137-7

The purpose of this circular is to provide information to aircraft and aerodrome operators with regard to the selection and development of noise abatement departure procedures designed according to the guidance in PANS-OPS, Volume I. Quantitative information regarding the effects of noise abatement departure procedures on noise and gaseous emissions are provided for a limited number of today’s commercial transport jet aircraft. The scope of this document is limited to noise abatement departure procedures that can be operated with aircraft currently in service.

The circular contains a number of references and details related to environmental interdependencies.

The analysis in the document demonstrates the noise, fuel, and emissions interdependencies of different Noise Abatement Departure Procedure (NADP) designs. Initial power cutback height has a significant influence on noise in terms of both location and amount of reduction in those areas, while also having an impact on fuel burn, CO2, and NOx emissions. The results in Chapter 5 show that higher cutback height leads to higher noise close in to an airport, but reduced noise farther out (due to steeper climb), though “distant” noise differences are considerably smaller than “close-in”. Meanwhile, higher cutback height generally showed increased NOx, but reduced CO2. The document concludes that, of the procedures included in the study, no single NADP minimizes overall noise and emissions simultaneously, and that trade-offs must be made between close-in versus distant noise, NOx versus CO2 emissions and, finally, noise versus gaseous emissions.

Links to information contained in:

•ICAO Doc 8168 Volume 1 – Procedures for Air Navigation Services – Aircraft Operations (PANS-OPS)
•ICAO Doc 9888 – Noise Abatement Procedures: Review of Research, Development and Implementation Projects - Discussion of Survey Results
•ICAO Doc 9931 – Continuous Descent Operations (CDO) Manual
Guidance on the Balanced Approach to Aircraft Noise Management (Doc 9829)Interdependency / Interdependencies, Noise
Doc 9829 | 2008 | Second edition | ISBN 978-92-9231-037-0

The aim of this guidance material is to provide States with advice and practical information on implementing a Balanced Approach to noise management. The Balanced Approach, which was adopted by the ICAO Assembly in 2001, encompasses four principal elements: reduction of noise at source, land-use planning and management, noise abatement operational procedures and operating restrictions on aircraft. This guidance material describes some of the measures available under each element, their interrelationship, and the tools that might be used to assess and compare their costs and benefits.

As a result, the Balanced Approach provides an internationally agreed approach to address aircraft noise problems where they occur, in an environmentally responsive and economically responsible way. It also gives a flexible way to identify a specific noise problem and remedies that are targeted and tailored to the individual airport situation in a transparent process which should include cost-effectivity analysis. The document contains references to environmental interdependencies.

Although emissions are not a part of the Balanced Approach, Chapter 8 (specifically section 8.10) of this manual contains information about interdependencies of the four principal elements of the approach and identifies the trade-offs between noise emissions and air emissions from aircraft. This chapter describes the trade-offs that can apply between noise and CO2, noise and NOx, noise and other emissions, and also between different gaseous emissions. It acknowledges that noise abatement procedures aimed at providing benefits to the community surrounding an airport may nevertheless have a negative impact on aircraft emissions. Such an impact should be balanced against the benefits to the community in the form of reduced noise levels. The trade-offs from noise abatement procedures should not be disregarded unless it can be substantiated that the air emission requirements override the noise benefits of these procedures.

Links to information contained in:

•ICAO Doc 8168 Volume 1 – Procedures for Air Navigation Services – Aircraft Operations (PANS-OPS)
•Doc 9777 – Committee on Environmental Protection, Report of the Fifth Meeting
•ICAO Doc 9814 – Airport Planning Manual (Doc 9184), Part 2, Land Use and Environmental Control, Chapter 5 — Land-use Planning.
•ICAO Doc 9888 – Noise Abatement Procedures: Review of Research, Development and Implementation Projects - Discussion of Survey Results
ATS Planning Manual (Doc 9426)Interdependency / Interdependencies, Interrelationship / Interrelationships
Doc 9426 | 1984 | First edition | ISBN 92-9194-664-8 

This manual consists of guidance material previously contained in Annex 11 and the PANS-ATM, and, consequently, supplements the provisions governing ATS as specified in these documents as well as in Annex 2. The manual not only contains information which can, or should, be taken into account in the formulation of development programmes within States or regions, but also material which can, or should, be applied directly to the planning and operation of the ATS system.

The Manual contains information on both environmental plus non-environmental interdependencies and is split into a number of parts.

Part 1 “Planning Factors / Section 1 How To Develop An Air Traffic Services Plan” notes in Chapter 1 “Factors Affecting Planning”, that sound planning is important to provide policy guidance on many issues significant to the efficiency of the ATS system including the determination in advance of likely environmental problems and methods of resolution. It also notes the need for special study at an early stage in ATS planning in respect of the effect of aircraft noise and atmospheric pollution onto the area exposed to these impacts. Chapter 2 “Establishment and Maintenance of the ATS Plan” notes that a periodic review should be incorporated into the planning programme from the outset. Planners should be alert to environmental changes as they occur. Chapter 4 “ATS Routes” and Chapter 5 “Alignment of ATS Routes”, highlights that trade-offs occur between an aircraft operator’s requirement to fly the most direct route (except when severe weather phenomena are encountered) on the one hand and capacity, environmental and security considerations on the other.

Part 2 “Methods of application employed by Air Traffic Services / Section I”, highlights trade-offs between aircraft operator’s requirements / traffic demand and restrictions imposed for environmental reasons, i.e. night curfews at aerodromes, noise abatement procedures, in Chapter 1 “Air traffic flow management and flow control”.


Please note that, whilst every effort has been made to ensure that all ICAO documents containing relevant information on interdependencies have been identified in this website, there may be some that have been inadvertently overlooked and those listed here should not be taken as an exhaustive list.


If additional information on interdependencies in an ICAO document, environmental or environmental plus non-environmental, is found then please contact ICAO at env@icao.int giving details. That information will then be analysed and this website updated if appropriate. It is intended to update the list as, and when, required to ensure that further work within ICAO on interdependencies is captured in this site.


Note that the preservation of safety is, and will always remain, of paramount importance, and nothing in these documents shall take precedence over the requirement to maintain safe operation and control of aircraft at all times.

Share this page: