RESUMO
Several concepts have been presented in the literature which have the potential to predict the operational load on aircrews during long-distance flights. They are briefly described and applied to a flight duty pattern actually scheduled for an airline route. For each model relative and absolute difficulty grades for the different segments of the pattern are evaluated and compared. Relative ranking results in an excellent agreement between the various models. Absolute classification into "normal," "heavy," and "definitely severe" segments reveals less conformity. From our observations on this route, it is concluded that the index of Mohler's model reflects the most realistic load estimates. Finally, a new approach is introduced which considers duty period, night flying, number of transits, preceding layover time, and preceding time-zone transitions as those elements constituting a computable and essential part of the operational load.