Marc C. Gelhausen is a member of the scientific staff at the German Aerospace Center (DLR). His research interests include mathematical and econometric modelling, in particular air transport forecasts and airport capacity constraints. Peter Berster is a member of the scientific staff at the DLR. He has extensive expertise in the analysis and modelling of air transport supply and demand data. Dieter Wilken founded the air transport research group at the DLR, and is a member of the scientific staff. His research interests include air transport supply and demand in Germany and worldwide. Prior to DLR, he worked with the Organisation for Economic Co-operation and Development (OECD) on developing a European model for forecasting passenger transport.