Regional population was used as a predictor of personal passenger travel, and regional GNP was used as a predictor of business passenger travel and freight demand. Both the FESG and EDF models incorporate the underlying assumption that the chosen parameters are satisfactory predictors of aviation demand and that aviation markets eventually mature. There are large differences between the EDF and FESG models with respect to the development of emissions scenarios. These scenarios represent an industry perspective on likely future developments in fuel efficiency and NO x reduction technologies, as well as further potentials and limitations. The fuel efficiency technology element of the DTI scenario was similar in this respect, but a NO x technology scenario appropriate to stricter emissions regulations was assumed, in which subsonic engine research programs would deliver emissions levels similar to those targeted in the NASA HSCT program.
Additional assumptions are also important to the results of the scenario models.
In the EDF model, assumptions about the dates of market expansion and maturity and the ultimate capacity levels chosen for the economic regions strongly influence the outcomes. The FESG models used new, partly proprietary, information from industry as a base to project emissions in the year 2050. None of the 3-D gridded inventories for 2050 assume any changes in design that would alter the cruise altitudes of subsonic aircraft.