The main aim of this dissertation is to develop a strategic modelling tool to assess the provision of additional airport capacity in Britain, with a particular focus on London and the South East, using the Infrastructure Transitions Research Consortium’s Transport Demand and Capacity Assessment model. Airport capacity is principally set by the capacity of its terminal(s) and runways. Over time, some growth is expected. The Davies Commission is currently reviewing the case for additional airport capacity in the London area, either by building a new airport or by expanding existing airports. This growth might be offset by a fuel price increase. In Heathrow (LHR) and other airports in the South East England there might be suppressed demand and some of this demand is either going to move to other airports or remain suppressed. This phenomenon has not yet been included in the Infrastructure Transitions Research Consortium’s Transport Demand and Capacity Assessment model (ITRC model). This dissertation is analysing the current passenger demand and also attempts to assess the future demand and specifically to determine the results of the possible knock-on effects to the airports of the region. Further objectives of this study are: • To review the work of the Airport Commission and the related literature. • To review work on modelling the demand for and supply of airport infrastructure. • To adapt the ITRC model so as to incorporate cross effects between airports.