Leading vs Lagging Safety Indicators Explained

Leading vs lagging safety indicators are tools used within a Safety Management System in business aviation to understand how an operation is performing from a safety perspective. Lagging indicators show what has already gone wrong. Leading indicators provide insight into conditions and behaviors that exist before an accident, incident, or serious event occurs. Both are required for an effective SMS, and both are referenced implicitly throughout FAA 14 CFR Part 5 and ICAO Annex 19 expectations for safety assurance and performance monitoring.

In simple terms, lagging indicators measure outcomes, while leading indicators measure processes and precursors. A mature SMS uses both together. Relying on only lagging indicators limits an operator to learning after harm has occurred. Using leading indicators allows the organization to identify elevated risk and intervene earlier, often before an event crosses a reportable threshold.

This article explains what leading and lagging safety indicators are, how they differ, why they matter specifically in business aviation, and what effective use looks like in real-world operations.

What are safety indicators in an SMS?

A safety indicator is a measurable data point used to monitor safety performance. Within an SMS, indicators support the Safety Assurance pillar by helping the organization determine whether safety risk controls are effective and whether the system is operating as intended.

FAA Part 5 expects operators to establish processes to monitor operational data, identify safety trends, and take corrective action when needed. While the regulation does not prescribe specific indicators, it does require operators to define safety performance measures that are appropriate for their size, complexity, and type of operation.

ICAO Annex 19 introduces the concept of safety performance indicators and safety performance targets as part of a performance-based approach to safety management. Leading and lagging indicators are the practical tools used to meet those expectations.

What is a lagging safety indicator?

A lagging safety indicator measures events that have already occurred. These indicators reflect outcomes, usually after a failure, deviation, or loss has happened.

Common lagging indicators in business aviation include reportable accidents, incidents, runway excursions, ground damage events, maintenance errors discovered after release to service, and regulatory findings from audits or inspections.

Lagging indicators are valuable because they are usually objective and clearly defined. They provide concrete evidence that something in the system failed or did not perform as expected. They are also commonly used in regulatory oversight, insurance analysis, and historical trend reporting.

However, lagging indicators have an inherent limitation. They only appear after the fact. By the time a lagging indicator changes, the organization has already experienced an undesired outcome. For this reason, lagging indicators alone are not sufficient for proactive risk management.

What is a leading safety indicator?

A leading safety indicator measures conditions, behaviors, or system performance that may increase the likelihood of an undesired outcome if left unaddressed. These indicators focus on what is happening within the operation before an accident or serious incident occurs.

Examples of leading indicators include increases in hazard reports related to a specific operation, repeated unstable approach reports that do not result in incidents, procedural deviations identified during internal audits, elevated fatigue reports, incomplete training records, or delays in closing corrective actions.

Leading indicators often rely on internal data sources, such as hazard reporting systems, audit findings, training records, flight data monitoring trends, or maintenance reliability data. They require interpretation and context, which makes them more complex to manage than lagging indicators.

Despite that complexity, leading indicators are critical to the preventive intent of an SMS. They allow safety managers and accountable executives to see weak signals, emerging patterns, and system stressors before they result in harm.

How leading and lagging indicators work together

Leading and lagging indicators should not be viewed as competing approaches. They are complementary and should be used together within a Safety Management System in business aviation.

Lagging indicators help confirm that a risk control failed or that a hazard was not adequately managed. Leading indicators help identify whether risk controls are degrading or whether new hazards are emerging.

For example, a ground collision is a lagging indicator. Prior to that event, there may have been leading indicators such as repeated reports of congested ramp operations, unclear marshalling procedures, or inadequate wing-walker staffing. If those leading indicators had been monitored and acted upon, the lagging event may have been prevented.

An effective SMS uses lagging indicators to validate learning after events and leading indicators to drive proactive intervention.

Why this matters in business aviation operations

Business aviation operations often experience lower accident and incident rates compared to higher-volume commercial operations. While this is positive, it can also create a false sense of security if safety performance is judged only by lagging indicators.

A Part 91 flight department may go years without a reportable accident. A Part 135 operator may have minimal enforcement history. A Part 145 repair station may have few findings during external audits. None of these facts alone indicate that risk is being actively managed.

In lower-event-rate environments, leading indicators become even more important. They provide visibility into everyday operational risk that does not result in immediate consequences but may still erode safety margins over time.

This distinction is especially important when considering differences across Part 91, Part 135, and Part 145 operations. Part 135 operators are required to implement an SMS under FAA regulation, while Part 91 operators may adopt SMS voluntarily. Repair stations under Part 145 have different operational hazards and data sources. Each must define indicators that align with how risk actually manifests in their environment.

Real-world examples of leading and lagging indicators

Consider a Part 135 charter operator monitoring unstable approach events. A runway excursion would be a lagging indicator. However, an increase in stabilized approach criteria exceedances, even without incidents, is a leading indicator.

For a maintenance organization, a returned-to-service error discovered during an audit is a lagging indicator. Repeated procedural deviations found during internal inspections or incomplete work card documentation are leading indicators.

In a flight training environment, a student runway incursion is a lagging indicator. Rising reports of confusing signage, poor runway markings, or instructor workload issues are leading indicators.

In each case, the leading indicator provides an opportunity to act earlier, adjust procedures, provide training, or modify resources before a serious event occurs.

Common mistakes and misunderstandings

One common mistake is assuming that leading indicators are simply smaller versions of lagging indicators. Leading indicators are not near misses that happen to have better outcomes. They are signals of system performance, not reduced-severity outcomes.

Another misunderstanding is believing that more indicators automatically mean better safety oversight. An excessive number of indicators can overwhelm safety staff and dilute attention. Indicators should be meaningful, actionable, and tied to decision-making.

Some organizations also struggle with the subjective nature of leading indicators. Because they often rely on internal reports or trend interpretation, they can be dismissed as anecdotal or inconclusive. This mindset undermines the preventive intent of an SMS.

Finally, many operators collect data without closing the loop. Indicators are tracked, but no thresholds, targets, or response expectations are defined. Without a defined management response, indicators become passive reports rather than active safety tools.

What good implementation looks like

When leading and lagging indicators are implemented effectively, they are clearly defined, reviewed regularly, and integrated into management decision-making. Each indicator has an owner, a data source, and an understood purpose.

Good practice includes defining acceptable ranges or trigger points for indicators, even if they are qualitative. It also includes reviewing indicators in safety review boards or management meetings, not just within the safety department.

A well-functioning SMS demonstrates that leading indicators drive preventive action, while lagging indicators drive system learning. Over time, this approach shifts the organization from reactive compliance toward continuous improvement.

How technology supports safety indicators in SMS

Modern SMS platforms support the use of leading and lagging indicators by centralizing data, enabling trend analysis, and reducing manual effort. Technology helps aggregate hazard reports, audit findings, and operational data into meaningful dashboards that support timely decision-making.

Technology does not replace professional judgment, but it does make it easier to identify patterns that would otherwise be missed. This is particularly valuable in smaller organizations where safety responsibilities are combined with other operational roles.

When used appropriately, SMS software supports the intent of FAA Part 5 and ICAO Annex 19 by making safety performance monitoring more consistent, transparent, and sustainable.

Summary and forward-looking perspective

Leading vs lagging safety indicators explained in simple terms highlights a core principle of Safety Management Systems in business aviation. Lagging indicators show what has already happened. Leading indicators help prevent what has not yet occurred.

An effective SMS uses both, tailored to the operation’s size, complexity, and regulatory environment. As business aviation continues to adopt performance-based safety management, the ability to interpret and act on leading indicators will increasingly define SMS maturity.

Organizations that invest in understanding and applying both types of indicators are better positioned to manage risk proactively, support informed leadership decisions, and maintain resilient operations over time.