Gray swans are events that are unusual but have identifiable signs and a reasonable chance of occurring. In aviation safety they sit between everyday risks and true surprises — not purely unforeseeable, but not routine either. Understanding gray swans helps flight operations, maintenance, and safety teams move from reactive fixes to proactive management. This article explains what gray swans are, how they differ from black swans, and how operators can build systems and processes to recognise and mitigate them. The guidance aligns with international safety management expectations and practical compliance steps you can adopt now.
What gray swans are, and how they differ from black swans
Black swans are rare, extreme events that are unpredictable and often only explained in hindsight. Gray swans, by contrast, are plausible and partly visible in data, behaviour, or environment before they happen. In aviation, a gray swan might be a new mode of equipment failure emerging from a design change, a predictable but accelerating cyber threat, or a weather pattern shifting due to climate effects that increases runway excursions at a given airport. These are not daily occurrences, but they carry measurable likelihood and significant impact.
Regulators and standards recognise the need to manage both known and emerging risks. ICAO Annex 19 and associated ICAO Safety Management Manuals encourage states and operators to use trend analysis and emerging risk monitoring. EASA and the FAA include requirements and guidance for Safety Management Systems (SMS) that expect organisations to identify and treat emerging hazards, including plausible but uncommon scenarios. Viewing gray swans as discoverable hazards helps satisfy these regulatory expectations while improving resilience.
Practical steps to identify and manage gray swans
Managing gray swans requires combining technical analysis, organisational processes, and practical resilience measures. Start by widening the sources you monitor: combine operational reports, maintenance trends, supplier information, industry safety data, and external signals like climate and cyber threat reports. Use scenario-based risk assessment to convert emerging signals into plausible event scenarios and run them through your risk controls and contingency plans. Techniques such as bow-tie analysis, functional resonance (FRAM), and human factors reviews help translate signs into action.
Make changes to your SMS to support gray-swan work. Introduce explicit emerging risk registers, assign ownership for signal monitoring, and set thresholds that trigger deeper investigation. Train teams to recognise weak signals during normal operations and to escalate them without fearing blame. Invest in predictive analytics where feasible, but do not rely only on algorithms: combine quantitative models with expert judgment and frontline feedback.
Actions that specifically strengthen resilience include reviewing redundancy and manual fallback procedures, updating training and simulator scenarios to include plausible gray-swan events, and exercising cross-department coordination (flight operations, maintenance, safety, IT, supply chain). Ensure your supplier oversight and configuration management processes detect design or manufacturing trends that could produce systemic risks. If you need a simple checklist, focus on four things:
- Broaden monitoring to include non-traditional signals and industry-wide sources.
- Use scenario-based assessment to test controls against plausible events.
- Embed emerging risks into SMS governance and reporting channels.
- Exercise and revise contingency plans and training to build resilience.
Document changes and lessons learned so regulators and auditors can see how you meet SMS requirements. When referencing regulation, consider ICAO Annex 19 and the ICAO Safety Management Manual for international guidance, and consult EASA Acceptable Means of Compliance or FAA advisory material for regional implementation details. For cyber-related gray swans, align with ICAO provisions on cyber resilience and regional regulatory guidance such as EASA’s cybersecurity recommendations.
Managing gray swans is not about predicting every odd event; it is about creating structured attention to the likely-unexpected so your organisation can adapt quickly and maintain safety. Embed horizon scanning into day-to-day SMS work, validate signals through multidisciplinary review, and keep practical contingency measures current. By doing this you meet regulatory expectations and reduce the chance that a plausible risk becomes a serious incident.
Conclusion
Recognise gray swans as plausible, partly-visible risks that deserve explicit treatment in your SMS. Establish processes to detect weak signals, translate them into scenarios, and validate controls through exercises and training. Keep documentation and governance aligned with ICAO, EASA, or FAA guidance so safety and compliance go hand in hand.