Implementation of Karolinska sleepiness scale to improve pilots awareness and confidence in fatigue reporting

Fatigue among pilots in short-haul, multi-sector night freight operations remains a critical challenge to aviation safety. Irregular schedules and prolonged exposure to the Window of Circadian Low (WOCL) cause cognitive impairments, slower reaction times, and reduced situational awareness. Despite regulatory frameworks such as Fatigue Risk Management Systems (FRMS), cultural and organisational barriers, including fear of punitive action and lack of standardised tools, continue to limit effective fatigue reporting. This study investigates the use of the Karolinska Sleepiness Scale (KSS) as a subjective fatigue management tool in short-haul night freight operations. A mixed-methods approach was applied, combining a six-week survey with semi-structured interviews. The study provides the first systematic evaluation of the KSS not only as a fatigue measurement instrument but also as a communication tool that bridges the gap between pilot experience and FRMS reporting practices in short-haul night freight operations. Pilots used the KSS during operational duties to assess fatigue levels and evaluate its influence on awareness and reporting practices. Findings indicate that the KSS improves pilots’ ability to recognise and communicate fatigue, supports proactive workload management, and fosters collaboration within crews. However, organisational gaps remain, including the absence of integration into Standard Operating Procedures (SOPs), lack of structured training, and hesitancy among less experienced pilots without formal company endorsement. The study recommends the formal adoption of the KSS into SOPs, supported by recurrent training and feedback mechanisms, together with integration of objective measures such as biometrics. Results highlight the potential of the KSS as a cornerstone of fatigue risk management and emphasise the importance of supportive safety cultures in prioritising pilot well-being as a key component of operational safety. • First empirical evaluation of the Karolinska Sleepiness Scale (KSS) in short-haul, multi-sector night freight operations. • Shows KSS functions as both a fatigue measurement tool and a communication aid for fatigue reporting. • Mixed-methods study combining a six-week operational survey with semi-structured pilot interviews. • KSS use increases pilots' fatigue awareness and confidence in reporting, especially among less-experienced pilots. • Recommends integrating KSS into SOPs and FRMS, supported by training and complementary objective fatigue measures.