# 18Comparing FAM and IFAM

## 18.1 Problem Definition

To illustrate the benefits of using the itinerary‐based fleet assignment model (IFAM) over the basic fleet assignment model (FAM), the same example given in Chapter 17 is solved using the basic FAM. As illustrated earlier, the main difference between the two models is that the FAM model is formulated at the flight level, while the IFAM model is itinerary based. As given in Chapter 11, the objective function of the basic FAM minimizes the sum of the flights operating cost and the spilled revenue (i.e. *C* + *S*^{′}), where *C* represents the operating cost and *S*^{′} represents the spilled revenue at the flight level. The problem constraints include the flight coverage constraints and the balance constraints. To match the settings of the IFAM problem, the resources availability constraints are ignored. Similar to the IFAM example given in Chapter 17, the basic FAM problem is formulated using the Excel Solver. Figures 18.1 through 18.10 present the problem solution steps in formula and value formats.

As shown in Figures 18.1 and 18.2, column B (rows 4–9) gives the list of flights in the network. Each flight is defined by its origin–destination pair. Columns C and D give the operating cost associated with assigning each of the six flights to fleet types *e*1 and *e*2, respectively. These cost elements are identical to the ones given in the IFAM example in Chapter 17. Column B (rows 10–12) also represents the remaining‐overnight (RON) arcs for the ...

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