Investigation level

Investigation types  

The ATSB directs its investigation resources to those incidents and accidents with the greatest potential of identifying systemic issues in aviation, marine and rail transport operations.

To ensure the best possible safety outcome in line with available investigative resources the ATSB conducts different types of investigations according to the anticipated scope and scale of the work required to determine the underlying cause of a safety occurrence. As evidence is collected and analysed the type of investigation can change to accommodate any additional activity required to do this.  

Short, defined, complex and major investigations are conducted under the auspice of the Transport Safety Investigation Act 2003 (TSI Act)

Occurrence briefs

Occurrence briefs provide the opportunity to share safety messages and information with industry and the public in the absence of an investigation. ATSB Transport Safety Investigators and members of the Safety Reporting Team produce the concise reports using information gathered during the notification process and an initial follow-up with relevant parties.


Short investigations provide a summary and analysis of commonly occurring transport safety accidents and incidents. Investigation activity includes sourcing photos and documentation of any transport vehicle damage and/or accident site, interviews of involved parties, collection of documents such as procedures and internal investigations by manufacturers and operators.

Short investigation result in a report of up to eight pages including a description of the sequence of events, limited contextual factual information, a short analysis and findings. Findings include safety factors (the events and conditions that increased the risk of incident or accident happening) but only examines the actions and conditions directly relating to the occurrence and any proactive safety actions taken by industry.


Defined investigations seek to identify systematic safety issues that reveal underlying cause of the accident. They involve several ATSB resources and may involve in-the-field activity or be an office-based investigation. Evidence collected can include recorded flight and event information, multiple interviews, analysis of similar occurrences, and a review of procedures and other risk controls related to the occurrence.

Defined investigations result in a report of up to 20 pages and look at transport safety accidents and incidents of a more complex nature than short investigations. They include an expanded analysis to support the broader set of findings within the report and may include safety factors not relating directly to the occurrence. Defined investigations may also identify safety issues (safety factors with an ongoing risk) relating to ineffective or missing risk controls. The report also identifies safety issues, along with proactive safety action taken by industry and ATSB safety recommendations.


Systemic investigations can involve in‑the‑field activity, and a range of ATSB and possibly external resources. They have a broad scope and involve a significant effort collecting evidence across many areas. The breadth of the investigation will often cover multiple organisations. Occurrences and sets of transport safety occurrences investigated normally involve very complex systems and processes.

In addition to investigating failed and missing risk controls, systemic investigations may also investigate the organisational processes, systems, cultures and other factors that relate to those risk controls, including from the operator, regulator, certifying and standards authorities. Systemic investigations result in substantial reports, often with several safety issues identified.

Systemic investigations were previously known as 'complex' investigations. The change in terminology more accurately reflects the broad scope and systems-level complexities involved in these investigations.

Major investigations

Major investigations are reserved for very significant accidents and are likely to involve significant ATSB and external resources and are likely to require additional one‑off government funding. They result in a comprehensive report.


Last update 02 September 2021