Reply To: Cost index calculation

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Armando Gonzales

Hi Daniel,
A few thoughts:
* You are correct that crew costs MAY have a time-related component, but salary structures vary from airline to airline. Further, some elements of the time-costs are non-linear “step functions,” so there is no “one size fits all” rule. You would have to develop an airline-specific model that considers the crew cost-model of that airline.
* The FMC cost index function (on larger airplanes) is not intended to account for post-flight delay costs. These costs are also non-linear and include step functions. In any event, for the typical mission ranges that today’s E-jets fly, it is unlikely the difference between MRC and MMO will be able to recover even a short delay.
* The simple conclusion: it is likely best to target a speed somewhere between min fuel and LRC. On shorter flights (1-3 hrs), it usually makes sense to target fuel efficiency as those costs will likely dominate.