Understanding the Root Cause in Aviation Safety and Compliance: From Symptom to System

By Florin Necula, PhD, MSc Airworthiness, B1 Licensed Aircraft Engineer, Maintenance Manager

Oct 26^th, 2025

1. Introduction: Why Root Cause Matters More Than Ever

Across aviation — whether in flight operations, airworthiness, safety management or maintenance — professionals encounter non-compliances, incidents and audit findings every day.

The natural question is: “What happened?”

But the more important question — the one that determines whether safety truly improves — is: “Why did it happen?”

The ability to identify root causes is what distinguishes a compliant organization from a learning organization.

Root cause analysis (RCA) transforms findings into improvements, prevents recurrence, and underpins both regulatory compliance and sustainable safety performance.

2. The Evolution of Root Cause Thinking

The idea of digging beneath symptoms to find underlying causes has its origins in industrial quality and reliability engineering. Techniques such as Fault Tree Analysis (FTA) were pioneered by Bell Labs in the 1960s to understand system failures in aerospace programmes.

In aviation, the concept was reshaped by human factors research and systems thinking. James Reason’s Swiss Cheese Model (1990) reframed accidents as the alignment of latent organisational weaknesses rather than isolated errors. Later, Wiegmann and Shappell’s Human Factors Analysis and Classification System (HFACS) formalised this approach, mapping unsafe acts to supervisory, organisational, and systemic precursors (Wiegmann & Shappell, 2003).

Other high-reliability sectors — such as nuclear, maritime and healthcare — adopted similar systemic frameworks, reinforcing that “human error” is often a symptom of system design.

3. Defining “Root Cause”: Beyond the Human Error Narrative

A root cause is an underlying factor that, if removed or controlled, would prevent recurrence of the event.

It is distinct from:

• Symptoms — what we see (e.g. a valve failed, a checklist was incomplete).
• Immediate causes — what triggered the symptom (e.g. fatigue, tool misuse, incorrect data entry).
• Root causes — why those conditions existed (e.g. schedule pressure, unclear procedures, poor training system, inadequate defences).

In aviation, attributing an occurrence to “human error” alone is inadequate.
Regulators and research institutions (e.g. FAA, EASA, ICAO) stress that error is the starting point of investigation, not its conclusion. Understanding the conditions under which humans err is the key to prevention (Reason, 1997; Dekker, 2011).

4. Methods and Tools for Root Cause Analysis

Aviation organisations use a range of structured RCA techniques, depending on complexity, data availability and risk.

Method	Description	When Useful
5 Whys	Simple iterative questioning to reveal underlying causes	Quick investigations, small events
Fishbone (Ishikawa) Diagram	Categorises causes (People, Process, Equipment, Environment, Management)	Human factors and process analysis
Fault Tree Analysis (FTA)	Logic diagram tracing from top event to underlying failures	System failures, technical events
Bowtie Analysis	Links causes, event and barriers	Risk-based safety assessments
STPA (Systems-Theoretic Process Analysis)	Examines unsafe control actions within complex systems	Emerging technologies and automation
HFACS + RCA Hybrid Models	Integrates human and organisational factors with causal logic	Maintenance, operations, ground handling

Recent research (Tu et al., 2020; Mendonça, 2021) shows that combining human-factors taxonomies with traditional RCA yields deeper insight — especially in multi-layered aviation systems.

5. Root Cause in the Regulatory Context

EASA Framework

• Part-145.A.60 requires organisations to establish an internal occurrence-reporting system to collect, evaluate, and identify adverse trends and corrective actions (Regulation (EU) 1321/2014).
• Part-145.A.200 (Management System) mandates proactive hazard identification, risk management, and verification of the effectiveness of safety actions — in other words, continuous root-cause assessment.
• Part-CAMO.A.202 (for Continuing Airworthiness Management Organisations) similarly demands “analysis of findings to determine root cause and prevent recurrence.”

FAA Framework

• AC 120-92D (Safety Management Systems for Aviation Service Providers) defines “system assessment and corrective action” as key elements of safety assurance — requiring the operator to identify and mitigate root causes of safety issues.
• FAA Order 8000.369C establishes the FAA SMS policy with the same focus on underlying causes.
• The U.S. Department of Transportation OIG (2021) found that several major carriers failed to identify root causes in maintenance oversight, resulting in repetitive non-compliances — a clear sign of systemic investigation gaps.

In short: regulators expect not just that problems are fixed, but that the system learns why they occurred.

Root cause identification, therefore, is both a compliance requirement and a measure of organisational maturity.

6. Human and Organisational Factors: The Hidden Layers

Aviation systems are socio-technical: technology, procedure, and humans interact under operational pressure. Reason (1990) distinguished between active failures (errors at the front line) and latent conditions (systemic weaknesses such as poor design, supervision, or culture).

Common latent contributors include:

• Ambiguous procedures or documentation
• Time pressure and operational demands
• Fatigue and circadian disruption
• Ineffective change management
• Communication and handover gaps
• Inadequate supervision or feedback mechanisms

Empirical studies (Harper, 2023; Tu et al., 2020) confirm that these organisational factors dominate maintenance, operational and flight safety events alike.

The message is consistent: human error may initiate an event, but organisational factors determine whether it becomes consequential.

7. Practical Application Across Aviation Functions

Whether in maintenance, flight operations or ground handling, a robust RCA follows a structured path:

1. Define the problem clearly – What exactly happened? When, where and under what context?
2. Collect and validate evidence – Data, logs, interviews, environmental and organisational context.
3. Map the timeline – From normal operations to event; identify deviations.
4. Identify failed defences – What barriers should have stopped the event?
5. Analyse causes – Use appropriate RCA tools; consider both human and system factors.
6. Determine root causes – Probe “why” until systemic enablers are exposed.
7. Develop corrective and preventive actions (CAPA) – Address causes, not symptoms; define accountability and timelines.
8. Monitor effectiveness – Evaluate recurrence, audit outcomes or safety indicators.
9. Share and learn – Feed lessons into safety meetings, SMS databases and training.

This cycle transforms compliance findings into organisational learning.

8. Repetitive Findings and Their Connection with Root Cause

One of the clearest indicators of weak root-cause discipline is the presence of repetitive findings — recurring non-compliances or incidents that persist despite previous corrective actions.

Why repetitive findings occur

• The initial investigation stopped at the immediate cause (e.g., “human error”) rather than the systemic one.
• Corrective actions targeted symptoms (e.g., retraining) rather than organisational conditions.
• Effectiveness monitoring was absent or superficial.

Regulatory expectations

• Under EASA 145.A.200, organisations must verify the effectiveness of actions — meaning they must ensure recurrence has been prevented.
• Under FAA AC 120-92D, safety assurance processes include “analysis of data to detect trends and identify systemic hazards.”

Practical management of repeat findings

• Maintain a repeat-finding register or trend report to track recurrence by category.
• Escalate repeated findings for deeper root-cause review (e.g. system design, culture, supervision).
• Treat repeat findings as indicators of latent organisational weaknesses.
• Link repeat-finding analysis to SMS performance indicators and management review.

In essence:

Repetition is the symptom; the absence of an effective root-cause process is the disease.
When the same issue resurfaces, the system is signalling that the underlying cause remains unresolved

9. Measuring Success: From Paperwork to Performance

How can an organisation know that its RCA process is effective?

Some indicators include:

• Decline in recurrence of similar findings or incidents
• Improved audit closure rates and CAPA completion
• Cross-functional sharing of lessons learned
• Reduced “human error” categorisation without deeper context
• Regulator confidence in investigation quality

Conversely, weak RCA is often characterised by “train and retrain” solutions, lack of follow-up and repeat findings — symptoms of a compliance culture, not a safety culture.

10. Cross-Industry Lessons and the Future of RCA

Other safety-critical domains provide valuable insight:

• Healthcare adopted RCA from aviation but later recognised the need to integrate human factors science to achieve real improvement (Peerally et al., 2017, BMJ Quality & Safety).
• Nuclear and rail industries apply systemic event analysis, focusing on organisational learning rather than individual blame.

Emerging trends in aviation include AI-assisted text mining of safety reports and knowledge-graph modelling for causal pattern recognition (Cai et al., 2024, Applied Sciences).
These tools may soon enhance how we identify and prioritise systemic root causes.

11. Conclusion: From Compliance to Competence

Understanding the root cause is not about assigning fault — it is about understanding how complex systems drift toward failure.

For aviation professionals — whether maintaining, operating, regulating or managing safety — the challenge is to ask deeper questions, seek systemic explanations and implement meaningful change.

In a high-reliability industry, true compliance is the natural by-product of competence, learning and curiosity.

Each event investigated is not merely a regulatory requirement; it is an opportunity to strengthen the system that keeps aviation safe.

References

• Cai, W., Zhang, W., Zhang, Y., et al. (2024). Knowledge Graph-Based Accident Causation Model for Aviation Safety Analysis. Applied Sciences, 14(16), 6887. https://doi.org/10.3390/app14166887
• Harper, R. (2023). Maintenance Errors: Human Factors and Causal Elements in U.S. Carrier Maintenance Operations. Collegiate Aviation Review International, 41(1).
• Reason, J. (1990). Human Error. Cambridge University Press.
• Reason, J. (1997). Managing the Risks of Organizational Accidents. Ashgate.
• Shappell, S. A., & Wiegmann, D. A. (2003). A Human Error Approach to Aviation Accident Analysis. Ashgate.
• Tu, J.-Y., Yong, J.-L., & Hwang, S.-L. (2020). A Latent Human Error Model in Aviation Maintenance Tasks. In Advances in Ergonomics in Manufacturing (AHFE Int.). https://doi.org/10.54941/ahfe100451
• U.S. Department of Transportation, Office of Inspector General (2021). FAA’s Oversight of American Airlines’ Maintenance Program. Report No. AV2021039.
• Wiegmann, D. A., & Shappell, S. A. (2003). A Human Error Approach to Aviation Accident Analysis. Ashgate Publishing.
• Peerally, M. F., et al. (2017). “The problem with root cause analysis.” BMJ Quality & Safety, 26(5), 417-422. https://doi.org/10.1136/bmjqs-2016-005511