The terrorist attacks of 11 September 2001 highlighted the vulnerabilities of airports and aircraft. Further attacks in 2002, 2007 and 2009, have led to major government reforms in passenger processing and airport access. The security of Australian airports has also followed this trend, with an increased police presence. However, limited consideration has been given to the costs of these measures, compared to benefit. This Working Paper identifies the factors to be considered in such cost-benefit analyses and the authors outline their preliminary findings. The scope for further research is highlighted, particularly in relation to risk analysis and cost.