CASA Part 139 is the Australian rule that determines what a certified aerodrome must do to operate safely, including running a functional safety management system. Part 139 sits within the Civil Aviation Safety Regulations (CASR), the broader set of rules used by CASA to regulate aviation safety in Australia. This guide covers what Part 139 requires, how the SMS fits into it and what the MOS adds beyond the rule itself. It also covers how to stay audit-ready without a last-minute scramble for evidence.
Key takeaways:
- Part 139 of CASR governs every certified aerodrome in Australia, including safety management. This obligation applies regardless of aerodrome size.
- An aerodrome SMS is built around ICAO Annex 19’s four components (Safety Policy, Safety Risk Management, Safety Assurance and Safety Promotion), given effect in Australia through CASR and the Part 139 MOS.
- CASA’s guidance material shows what a compliant SMS looks like in practice, but meeting Part 139 means demonstrating assurance (proof your controls are working now, not just evidence they once existed).
- A CASA surveillance can be scheduled or triggered without notice by a credible report. Continuous audit readiness beats scrambling to assemble evidence after the fact.
- Regional and council-run aerodromes carry the same Part 139 obligations as major airports, usually with far less capacity to manage them. This is where fragmented, manual evidence trails can hurt most.
What CASA Part 139 Covers
Part 139 of CASR sets out the requirements and standards for aerodromes with published instrument flight procedures. It includes aerodrome facilities, obstacle control, operational procedures and safety management. Part 139 of CASR and the accompanying Manual of Standards (MOS) have been in force for several years now, following extensive consultation with industry. CASA put runway condition reporting in place a couple of years ago. The rule itself is settled, but the detail behind it keeps evolving. CASA is considering further amendments to the MOS in areas driven by ICAO, including friction testing standards and changes to the PANS-Aerodromes document.
Where the SMS Fits
The requirement for an SMS comes from ICAO Annex 19 (Safety Management), the international standard that consolidates safety management provisions across aviation into a single framework. Annex 19 structures an SMS around four components: Safety Policy, Safety Risk Management, Safety Assurance and Safety Promotion.
For a breakdown of how these four components interact, see What Makes Up a Functional Aviation SMS?
The Part 139 Manual of Standards and CASA’s SMS Guidance
The Manual of Standards (MOS) that accompanies Part 139 sets the detailed standards an aerodrome must meet. Where Part 139 states the obligation, the MOS spells out the specifics, including facility standards, obstacle limitation surfaces and the requirements an SMS has to satisfy. CASA also publishes guidance material to help operators build and run an SMS. Its Multi-Part Advisory Circular AC 139.H-06 (jointly issued with several related ACs) includes guidelines for preparing a safety management system. It is written to keep SMS requirements consistent across several CASR parts rather than having each aerodrome interpret them separately. This is essentially guidance rather than law, but it’s the clearest picture CASA gives of what a compliant SMS looks like in practice.
Meeting Part 139 takes more than compliance, though. CASA expects assurance too, not just evidence that your SMS controls existed at some point, but confidence they’re working right now. As Carly Waddleton, Chief Customer Officer at OneReg, put it after working with dozens of airports: "The airports we work with that are seeing the strongest operational outcomes aren't simply digitising. They're building connected operational visibility. There's a difference."
For a deeper distinction between compliance and assurance, and what continuous audit readiness looks like in practice, see Compliance vs Assurance: What Continuous Audit Readiness Really Means.
Staying Ready for a CASA Surveillance
A CASA surveillance involves checking that a certificate holder continues to meet its Part 139 obligations.
CASA periodically visits sites where it has assessed risk with a particular operator, checking systems and products, reviewing documents and manuals and examining other available data. Unscheduled surveillance is also conducted when an operator comes to CASA’s attention through a credible report of alleged unsafe conduct, or via information from other aviation agencies. That’s the real payoff of a well-functioning SMS, as audit readiness stops being a separate exercise because you’re always ready. If evidence is current by default, it doesn’t matter whether the visit is scheduled or not.
What a CASA Surveillance Typically Looks For
- A clear evidence trail for how hazards and risks are identified, assessed and controlled.
- Corrective actions that are tracked to closure, not left open indefinitely.
- Manuals and procedures that reflect current practice, not just the version on file, and are actually used by staff.
- A risk register that’s being used, not just maintained for show.
What This Means for Regional and Council-Run Aerodromes
Regional aerodromes don’t automatically carry the same safety obligation as major airports. Under the Part 139 MOS, whether an aerodrome needs a full SMS, a risk management plan (RMP) or simply an SMS recommendation depends on its annual passenger and aircraft movements, not on being certified alone.
Aerodromes with 50,000 or more air transport passenger movements or 100,000 or more aircraft movements in a financial year must have an SMS (MOS Chapter 25). Below that, but at or above 25,000 passenger movements or 20,000 aircraft movements, a risk management plan is mandatory (MOS Chapter 26). Below both thresholds, an SMS is recommended but not required.
Many regional and council-run aerodromes sit in the RMP tier, or close to the thresholds where growth could move them into SMS territory. What doesn’t change with size is capacity. A regional or council-run aerodrome is more likely to be running its SMS or RMP with one or two people wearing several hats, which makes fragmented evidence and manual document control a bigger operational drag than it would be for a large operator with a dedicated compliance team.
Complete Regulatory Assurance for Australian Operators
OneReg was built by aviators, so the platform is grounded in the way an aerodrome actually runs. OneReg Co-Founder and Chief Customer Officer Carly Waddleton says the company built one configurable platform around Part 139 and the MOS for Australian operators, rather than adapting a generic system after the fact.
“The fundamentals of aviation compliance — risk-based oversight, evidence, traceability, who’s authorised to do what — are remarkably consistent whether you’re under the CAA, CASA, the GCAA, or others,” she says. “The differences lie in the specifics: form numbers, reporting cadence, exposition structures, language.”
In practice, OneReg provides real-time, role-based visibility of an operation’s compliance and risk posture against Part 139. An operations manager sees their site and an executive sees the aggregated picture across several aerodromes. With continuous audit readiness in place, a CASA surveillance becomes a formality, not a scramble. It’s highly configurable, so your workflows can be updated as they evolve without a technical project, and your historical data stays intact through every change.
See OneReg in Action
CASA Part 139 sets the obligation, the Manual of Standards sets the detail and the operations manager meets the requirements through their SMS. It’s not a document on a shelf, but the daily practice of identifying hazards, controlling risk and being able to show, at any moment, that it’s working. For Australian aerodrome operators, the last part is where most of the effort goes: not building the SMS, but proving it’s live. If you want to see what continuous audit readiness looks like for your operation, book a demo.
Frequently Asked Questions
What is CASA Part 139?
CASA Part 139 is the part of the Civil Aviation Safety Regulations (CASR) that sets the requirements and standards for certified aerodromes in Australia. It covers aerodrome facilities, obstacle control, operational procedures and safety management, and has been in force for several years alongside the Part 139 Manual of Standards.
Does CASA Part 139 require a safety management system?
Not automatically. Under the Part 139 MOS, an SMS is mandatory only for aerodromes with 50,000 or more air transport passenger movements, or 100,000 or more aircraft movements, in a financial year (MOS Chapter 25). Aerodromes below that, but at or above 25,000 passenger movements or 20,000 aircraft movements, must instead have a risk management plan (MOS Chapter 26).
Below both thresholds, an SMS is only recommended, not required, and CASA has issued dedicated guidance for aerodromes considering one.
The underlying requirement traces back to ICAO Annex 19, which CASA gives effect to in Australia through CASR and the Part 139 Manual of Standards.
What is the Part 139 Manual of Standards?
The Part 139 Manual of Standards (MOS) is the legislative instrument made under Part 139 that sets the detailed standards an aerodrome must meet. Where Part 139 states the legal obligation, the MOS spells out the operational specifics behind it.
What is a CASA surveillance?
A CASA surveillance is the regulator’s oversight activity used to check that a certificate holder continues to meet its obligations. CASA’s approach is risk-based, and it also conducts unscheduled surveillance when an operator comes to its attention through a credible report or information from another aviation agency.
Is CASA Part 139 the same as FAA Part 139?
No. CASA Part 139 is issued by Australia’s Civil Aviation Safety Authority and applies to Australian aerodromes. The FAA’s Part 139 is a separate US regulation covering US airport certification. They share a part number by naming convention, not by jurisdiction.
What are the four components of an aviation SMS?
The four components defined by ICAO Annex 19 are Safety Policy, Safety Risk Management, Safety Assurance and Safety Promotion. Safety Policy sets accountabilities; Safety Risk Management identifies and controls hazards; Safety Assurance checks those controls are working; Safety Promotion builds the training and culture that sustain the other three.
