However, the daily activity at each major airport can vary and most only handle a small amount of daily operations caused mainly due to the commercial airline's hub and speak system, most passengers are only routed through a small number of larger airports that will ultimately deliver them to their final destination. The hub and speak system operated by air carriers has led the NPIAS to further subcategorize primary airports into hubs based on the number of passengers on board (Young & Wells, 2011, p..