One of the services in GSE PROMOTE Stage II is the Support to Aviation Control Service, SACS for short. The aim of SACS is to deliver in near-real-time data derived from satellite measurements regarding SO2 and aerosol emissions possibly related to volcanic eruptions, and where possible to track volcanic plumes. In case of "exceptional SO2 concentrations", SACS will issue a notification by e-mail to interested parties. Together with information from other sources, data from SACS can assist official organisations - the Volcanic Ash Advisory Centres (VAACs) - when issuing alerts regarding volcanic activity to air traffic control and airline organisations, so as to help them to decide whether to reroute aeroplanes in case of volcanic clouds. This paper gives an overview of the background and structure of SACS and presents a few example results. More information and links to the data products (maps and data files) can be found via the SACS web portal http://sacs.aeronomie.be/ or via the PROMOTE website http://www.gse-promote. org/ under "special services".