This study assesses the economic importance of air transport and airport activities in Belgium in terms of value added, employment and investment over the 2009-2012 period 1 . The sector considered embraces not only the activities directly connected with air transport, but also all the activities that take place on site at the six Belgian airports (Antwerp, Brussels, Charleroi, Kortrijk, Liège and Ostend). The study reviews the direct and indirect effects of the sector on the basis of microeconomic data (mainly obtained from the Central Balance Sheet Office) and macroeconomic data (from the National Accounts Institute). It also includes an analysis of the social balance sheet and certain ratios using Central Balance Sheet Office data. In 2012, air transport and airport activities generated € 5.6 billion in direct and indirect value added (i.e. 1.5 % of Belgian GDP) and employed 66,200 people in full-time equivalents (FTEs) either directly or indirectly (1.7 % of domestic employment). Brussels Airport is the country’s biggest airport in terms of passenger traffic, but has seen its leading position somewhat eroded by Charleroi, which with Ryanair has staged robust growth in the low-cost segment. Meanwhile, Liège has assumed the position of leading cargo airport and currently accounts for over half of total cargo traffic to and from Belgium. Charleroi and Liège are the fastest growing airports in terms of value added and employment. With the exception of Ostend, the Flemish regional airports have also proved resilient on both counts, while Brussels Airport may be described as holding more or less steady.