ABSTRACT
Traffic is the first of four elements in the operating performance model around which Part 2 of the book has been structured:
'Demand' is the quantity of a product that customers are willing and able to purchase at a particular price over a defined period of time. 'Traffic' is that part of demand for air transport services that has been satisfied by carrying passengers and cargo; it is distinct from demand that has not been satisfied - demand that has been 'spilled', perhaps because space was not available when required and no alternative was acceptable. We will see in Part 3 of the book that 'spill' is a concept critical to network, fleet, and revenue management, and that 'spill models' are used in these functions. Nonetheless, the industry as a whole can only estimate rather than measure spill, and there is a tendency to treat 'demand' and 'traffic' as synonymous; in this book they are kept separate, with traffic treated as a subset of demand.
