Arising from a cost benefit analysis (CBA) the benefit to costs ratio for Galileo is 4·6 – very high for an infrastructure investment project. A substantial proportion of the user benefits arise from the aviation sector and the estimates are described in Galileo documents as ‘conservative’ and ‘unquestionable’. This paper analyses the calculations used to support the benefits to aviation and examines the questionable assumptions and statements that are shown to be based on an incorrect understanding of the air transport sector. The paper concludes that the aviation benefits could be considerably overstated and that an analysis, more soundly based on airport operations, air traffic control and future strategic changes, is required.