This Working Paper assesses the economic importance of the air transport sector in Belgium in terms of value added, employment and investment over the period from 2007 to 2009. The study is an update of an analysis carried out by the Bank in 2009 (Working Paper No. 158). The air transport sector under review spans not only activities directly linked to air transport, but also all business undertaken on the sites of Belgium's six airports (Antwerp, Brussels, Charleroi, Kortrijk, Liège, Ostend). Both the direct and indirect effects of the sector are estimated respectively on the basis of microeconomic data (drawn mainly from the Central Balance Sheet Office) and macroeconomic statistics (from the National Accounts Institute). The study also includes an analysis of the social balance sheet and looks into some financial ratios on the basis of data from the Central Balance Sheet Office.