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The four principles of an Aviation Safety Management System (SMS)

Apr 15th 2019
The four principles of an Aviation Safety Management System (SMS)

Although their details will change subtly from organisation to organisation, the main four principles of a aviation safety management system (SMS) are:  

These four components (which in turn are broken down into twelve elements) are listed in ICAO Document 9859 and it is likely that you are already familiar with them, particularly if you have implemented your own SMS by now.

The following article examines how each of these four components should be developing in your organisation by asking a number of questions that might be phrased by your NAA inspectors as they seek to determine if your SMS is delivering your stated safety objectives and is improving continuously as part of the Performance Based Oversight objectives discussed in Annex 19, Revision 1.


  • Is your safety policy widely available and is the workforce fully engaged and supportive?
  • Do the workforce appreciate the importance of hazard identification and safety reporting?
  • Is adequate and timely feedback provided to the reporters?

These three questions apply across the entire organisation and are not confined to Flight Operations. This can only be achieved if management are likewise engaged and empowered to deliver the safety policy. What evidence is available to demonstrate your enterprise approach to safety management? Items such as an increase in voluntary reporting rates for all departments can be used. Furthermore, the establishment of a Just Culture (ASAP in the USA) must be evidenced and must be used by management at all levels.


Risk management

  • Does your safety reporting system allow employees to submit hazard reports easily? If the system is complex or not easily accessible, the workforce will be reluctant to submit reports.
  • Are the reports acted upon and is feedback provided to the reporters?
  • Are your risk registers up to date and accessible to management?
  • How is the efficacy of risk controls/mitigations monitored?
  •  Is there adequate resource in place to meet the requirements of implemented risk controls?
  •  Do you have processes in place to address both safety issue risk assessments and management of change?
  • Does your risk process recognise that safety is only one part of the risk picture? Do you assess risks in terms of their impact on financial, reputation and environmental factors?
  • Finally, how are risks communicated to the general workforce? Do you use diagrammatic representations such as Bow Tie visualisations that can be easily understood?

A primary objective of the risk control process should be to ensure that the appropriate resource is allocated to mitigate identified risks. Ideally, a register of all controls should be maintained alongside the risk register. All identified risks must be accepted by a responsible manager and high-level decisions should be made using risk-based analysis. Finally, there must be suitable processes in place to review and monitor all risks listed in the register as part of the assurance processes.



  • Are your risk controls implemented and effective?
  • Are controls reviewed regularly?
  • Is your SMS improving continuously?
  • Is your SMS delivering your stated safety objectives?
  • Have you agreed to operate to an Acceptable Level of Safety Performance (ALoSP) with your Regulator and can you demonstrate that you are achieving this?

This is a most important part of a SMS. Usually, the above requirements are met by the establishment of Safety Performance Indicators (SPIs) and Safety Performance Targets (SPTs). These items are discussed fully in Document 9859 (issue 4) and without these in place any organisation will find it difficult to demonstrate an ALoSP and continuous improvement of the SMS.


Unless the safety policy and its objectives are communicated widely and in a format that is designed to engage all employees, it is unlikely to be effective. Poster campaigns can be useful, but short lived. Management must promote the safety policy continuously. This could be in the form of monthly safety newsletters by fleet managers (which could be a leading SPI if used). Again, this process should be adopted across all departments and whilst safety promotion is often very good in the flight operation:

  • Is it applied in all areas?
  • When did the commercial department last attend a risk assessment or a monthly safety meeting?

The quotation below is by William Voss (past CEO of the Flight Safety Foundation). It encapsulates how an effective SMS should function and also demonstrates the need for good safety promotion across an organisation:

“Go back to last year’s budget and see if you can find one single instance where information from your SMS caused you to spend money differently to how you had planned. If you cannot find an example of that in your operation you either have an extraordinarily brilliant budgeting process or your SMS is not delivering. I would bet on the latter.”

Safety management systems are more than just four principles

To ensure that your organisation implements an effective safety management system, you need to be able to monitor continuously each aspect of your system and question whether your implemented processes are as effective as they could be.

Of course, a safety management system is more than just the four principles above. In fact,  a safety management system encompasses so many more aspects that need to be considered by airlines. To help put this in further perspective, we have created a comprehensive guide that explores everything that makes up an effective aviation safety management system. It also looks at how airlines can add value by implementing a much more efficient system that could provide a myriad of benefits including improved compliance, increased reporting and best of all, promoting a just safety culture.

Download our free insight ‘ The Essential Guide to Aviation Safety Management Systems’ now to learn more.


Image by permission of Deresh Pillay on Unsplash