In some parts of the world, particularly in North America and Europe, the airway and airports system is currently operating under constraints that limit its ability to provide service. These constraints are likely to become more acute in the future as the demand for aviation services continues to grow. Congestion resulting from capacity constraints impairs the economic and environmental performance of airlines and the entire aviation system. To accommodate future demand, physical and technological infrastructure must be upgraded and expanded. It is therefore important to note that the traffic forecasts reviewed in this chapter are all unconstrained forecasts that do not evaluate system capacity constraints when estimating future traffic growth.
Aviation also depends on petroleum fuels.
Oil companies predict continued supply of their raw material, and kerosene supplies should have similar availability as the present day. The long-term scenarios assessed for this report implicitly assume continued availability of fuel at moderate prices. The effects of an HSCT fleet are considered in Section 9.5 . Although none of the long-term scenarios reviewed here is considered impossible, some may be more plausible than others. We devised three simple checks to assess plausibility.