Did you know Swiss cheese changed the way we think about aviation safety?

One afternoon, while preparing tea, psychologist and human factors expert Professor James Reason had a thought that would revolutionise accident prevention across industries. His "Swiss Cheese Model" transformed how aviation – and many other fields –  approach safety,  by shifting the focus from individual blame to system-wide safeguards.

At its core, the Swiss Cheese Model shows that accidents rarely occur because of a single mistake. Instead, they happen when multiple failures align across different levels of an organisation. To visualise this, imagine several slices of Swiss cheese stacked together. Each slice represents a layer of defence, such as:
•    Pilot training
•    Aircraft maintenance
•    Air traffic control protocols
•    Safety management systems

The holes in each slice symbolise weaknesses in those defences. When the holes align, an error can pass through all layers and cause an accident.

The key insight is that accidents happen when the holes in each slice of cheese line up, allowing an error or hazard to pass through all the defences and cause an accident.

A new approach to safety

Prof. Reason's work shifted the aviation industry's focus from assigning blame to individuals for accidents or mistakes, to focusing on strengthening the entire safety system. And he highlighted the importance of a comprehensive safety culture, which aviation safety organisations and manufacturers define through key elements like:

• a reporting culture, so that operators and managers have knowledge of factors that determine safety levels;
• a just culture, so people are encouraged to report safety-related information;
• a learning culture, where an organisation is willing to draw conclusions from its safety information system and implement reforms.

These elements ensure that everyone – from frontline staff to senior leadership – plays a role in maintaining and improving safety.

A lasting legacy

Prof. Reason's model has had a lasting impact on aviation, and many other industries. It's a reminder that safety is a collaborative effort, relying on the cooperation of individuals, groups, and organisations to create a robust and resilient system. This is why airlines, manufacturers, regulators, and international bodies like the ICAO work together to share safety information, develop best practices, and continuously improve the safety of air travel.

Recognising the value of the Swiss Cheese model, the International Civil Aviation Organisation (ICAO) adopted the model in the early 1990s as a conceptual framework for understanding and improving aviation safety. ICAO's adoption underscores the model's significance in shaping global aviation safety standards and practices.

Airlines, manufacturers, and regulators worldwide continue to apply James Reason’s principles to enhance safety management – recognising that safety is not just about technology – it's about people working together, sharing knowledge, and continuously improving systems.

At ASD, we know that ensuring the safety of air travel is based on ongoing collaboration across the whole aerospace ecosystem. By applying the principles that James Reason championed, we help ensure our industry continues to work together to protect passengers, crew, and the future of aviation.

So, the next time you board a plane, you can trust that countless layers of defence – inspired by a simple slice of Swiss cheese – are working behind the scenes to keep you safe.