Final answer:
A) Maximize load factors to keep planes full. The primary goal of Hub-and-spoke (HS) systems for airlines is to maximize load factors to keep planes full.
Step-by-step explanation:
The primary goal of Hub-and-spoke (HS) systems for airlines is to maximize load factors to keep planes full. By using a hub-and-spoke system, airlines can ensure that their planes are efficiently filled by having multiple flights arriving at and departing from a central hub airport at specific times. This allows passengers to connect between spoke cities with just one connection and increases the number of cities that can be served.