Foundations of operator state monitoring system development in aviation

The role and responsibilities of pilots have been evolving as advanced automation systems are being integrated for flight operations. Operator state monitoring (OSM) helps ensure safety and improve performance by detecting and predicting degraded operator state during operations. Despite growing interest in OSM, no unified framework exists that integrates impairment definitions, sensor criteria, and interface design requirements. This work is presented as a conceptual analysis that establishes a foundational framework for operator state monitoring system (OSMS) development, addressing what an OSMS should monitor, what types of operator state changes should be detected, the characteristics of sensing and communication needed to support these functions and the operational considerations that should inform future development. A literature review establishes potential impairment and incapacitation events for pilots, identifies relevant physiological features to support detection of these events, and assess the possible impact of such events on flight operations to inform a system response. Existing work concentrates on military and automotive contexts and on workload, fatigue, and drowsiness rather than the acute-event end of the impairment continuum; the framework developed here spans the normal to impaired to incapacitated range required for in-flight operations. OSMSs should be developed based on a multi-modal data approach consisting of physiological features, pilot performance and activity, aircraft state and environmental data, as well as contain a means for pilots to self-report input. Heart, breathing, and behavioral features are affected across the widest range of events, making them broad-coverage candidates for sensor selection, though breadth of coverage is distinct from diagnostic specificity and no single feature is treated as a standalone indicator. The remaining recommendations address the engineering of sensing and processing for the flight deck. Design guidance for the alert and notification interface is presented alongside the recommendations. As OSMSs mature, this framework can serve as a critical reference for developing robust, reliable, and widely accepted solutions in aviation.