This appendix summarizes the methodological approach of the Federal Aviation Administration (FAA) in preparing the terminal area forecasts (TAF) of demand for aircraft operations at terminal facilities. The approach is undergoing significant changes. Up to 2013, the TAF were prepared under an approach (referred to as Legacy TAF) that forecasts passengers and operations at individual airports. The approach applied in 2014 and beyond, called Terminal Area Forecast Modernization (TAF-M), focuses on forecasting passengers and operations at a finer level of granularity—at the level of origin–destination pairs, of routes serving specific airport pairs, and of flight segments connecting pairs of airports directly.
For commercial traffic, the Legacy TAF approach uses “passenger enplanements” as the starting point. For the 30 busiest airports (which together accounted for more than 70 percent of national enplanements in 2012), locally originating enplanements are forecast by coupling historical data with local-level forecasts of such input variables as personal income (or, more recently, disposable income), employment, population, and local fares. Enplanements of connecting passengers and of international passengers are forecast separately by considering the status of an airport (hub, nonhub, international gateway) and historical trends.
Forecasts of enplanements at second-tier airports (approximately 80) are obtained through a less detailed procedure relying primarily on econometric models. For the remaining roughly 390 towered airports, forecasts rely primarily on projections of historical trends and reviews of local conditions.
To convert enplanement forecasts to estimates of commercial air traffic activity, the number of aircraft departures is estimated on the basis of projections of aircraft characteristics (e.g., seating capacity, range) and of load factors. Short-term (1- to 1.5-year) forecasts of commercial aircraft operations are prepared for the busiest airports. They are strongly influenced by detailed information concerning recent-month and near-term projected flight schedules, aircraft mix, and so forth at the subject airport.
Forecasts of all-cargo flights rely primarily on projections of historical trends. They have been exhibiting a slow growth rate at an aggregate level during the past decade and account for a small percentage of air traffic activity in the United States.
Because of a relative paucity of data, forecasts of general aviation (GA) air traffic activity are primarily based on time-series models that are less advanced than those used for forecasting commercial traffic. In addition, GA, which is typically associated with smaller aircraft and recreational flying, has exhibited a high degree of volatility and has been hit particularly hard by the various economic downturns of the past dozen years. Business GA activity, especially activity involving jet aircraft, has been more stable, but even this segment was strongly affected by the financial crisis of 2008–2009 and has been recovering at a slow rate.