Problem
1. To simplify the analysis, assume for now that there is vir- tually no turnaround time between flights so the next flight can begin as soon as the current flight ends. (If an immediate next flight is not available, the airplane would wait until the next scheduled flight from that city.) Develop a network that displays some of the feasible routings of the flights. (Hint: Include separate nodes for each half hour between 8:00 AM and 7:30 PM in each city.) Then develop and apply the corre- sponding spreadsheet model that finds the feasible combina- tion of flights that maximizes the total profit.
2. Rachel is considering leasing additional airplanes to achieve economies of scale. The leasing cost of each one again would be $30,000 per day. Perform what-if analysis to determine whether it would be worthwhile to have 5, 6, or 7 airplanes instead of 4.
3. Now repeat part a under the more realistic assumption that there is a minimum turnaround time of 30 minutes on the ground for unloading and loading passengers between the arrival of a flight and the departure of the next flight by the same airplane. (Most airlines use a considerably longer turnaround time.) Does this change the number of flights that can be flown?
4. Rachel now is considering having each of the four airplanes carry freight instead of flying empty if it flies overnight to another city. Instead of a cost of $5,000, this would result in net revenue of $5,000. Adapt the spreadsheet model used in part c to find the feasible combination of flights that maxi- mizes the total profit. Does this change the number of air- planes that fly overnight to another city?