Assessment of pilot fatigue based on flight routes: Towards the determination of operational limits

This Bachelor's Thesis investigates pilot fatigue in long-haul operations with the specific objective of assessing the feasibility of operating the Miami-Barcelona (MIA-BCN) return flight with two pilots instead of the current three-pilot configuration. The study uses the BCN-MIA and MIA-BCN routes as a case study to analyse how crew composition, duty timing, rest opportunities and circadian effects influence fatigue and alertness levels. The analysis combines predictive alertness modelling, roster-level fatigue assessment and subjective pilot feedback. A biomathematical fatigue model implemented through the Crew Alert tool is used to evaluate predicted alertness at Top of Descent under different crew configurations and departure times. In parallel, a survey-based study collects subjective data on fatigue, sleepiness and alertness before, during and after flight. In addition, a comparative analysis of fatigue accumulation is performed at both flight and roster level to assess the impact of operating the MIA-BCN return flight with two pilots instead of three. The results show that reducing crew composition on the return flight leads to a decrease in fatigue and alertness margins, increasing exposure to fatigue-related hazards, particularly in the presence of circadian misalignment and long duty periods. While subjective and predictive indicators generally remain within acceptable operational limits under the current three-pilot configuration, the analyses indicate that a two-pilot operation would significantly reduce operational margins and increase sensitivity to schedule variations and delays. The study concludes that, although operating the MIA-BCN route with two pilots may be feasible under certain conditions, a definitive assessment would require the implementation of a fully validated Fatigue Risk Management System supported by biomathematical fatigue modelling. The findings highlight the importance of data-driven fatigue management in long-haul operations and provide operational insight to support informed decision-making regarding crew scheduling and fatigue mitigation strategies.