Mark G. Stewart and John Mueller. Are We Safe Enough? Measuring and Assessing Aviation Security

17.5 billion dollars. Between the Transportation Security Administration (TSA) budget, government agency expenditures, and the estimated opportunity costs of the travelling public’s delays and damages, this is how much we as a country put into aviation security in fiscal year 2016. Where does this money go? Why does it cost so much? Are we safe enough? Most importantly, is this cost worth it? In JohnMueller andMarkG. Stewart’s newbook,Are We Safe Enough? Measuring and Assessing Aviation Security, the authors explore the nature of aviation security in the USA. They cite official government reports, stories from the media, and comparisons to other country’s version of our Department of Homeland Security (DHS) and Transportation Security Administration (TSA). Using their consolidated data, they argue that “these considerations are particularly important because it certainly appears that avoiding overreaction is by far the most cost-effective counterterrorism measure.”1 The book attempts to determine the costs and benefits of transportation security spending, including those associated with potential changes to current screening methods. After defining the goals of the TSA and what constitutes a terrorist attack, the authors detail the 21 current layers of aviation security, breaking them down individually, and displaying how effective each layer is at deterring or disrupting a potential terrorist attack. They find that of the twomain terrorist threats, hijacking has approximately a 99.3% chance of being deterred or disrupted, and a passenger-borne bomb attack has a 98% chance of being deterred or disrupted. They conclude that “these levels of risk reduction are very robust” given the standard for acceptable risk.2 They further break down the cost of each layer. The authors use historical terrorist attack data from 1970 to the present as benchmarks for costs, both in lives and economic loss. This enables an analysis of costs that pertain specifically to aviation security. The authors compare the cost of each individual layer. They find that several layers, such as the hardened cockpit door and the Federal Flight Deck Officer program (FFDOs) are effective at preventing hijacking attacks at an exceptionally affordable cost. They also findmarginal cost-effectivemeasures – in regard to thwarting both hijackings and bombings – in the Visual Intermodal Protection Response (VIPR) teams, canine teams, and others. Some of the most expensive and cost-ineffective layers are found to be the Behavioral Detection Officers (BDOs) and the Federal Air Marshal Service (FAMS), as neither layer has been found to adequately protect hijackings or bombing threats. Transportation Security Officers (TSOs) and their duties at checkpoints and as travel document checkers (considered two separate layers) were not found to be cost-effective, either. However, the authors praised the creation of TSA PreCheck, arguing it allows for more efficient screening of nearly half of the traveling public, and more intensive screening of higher risk passengers, thus making overall aviation security safer.3 The authors use their findings on the BDO program and FAMS to argue for the reform or elimination of them, at a savings of hundreds of millions of dollars. They use data from other countries to argue for implementation and expansion of cheaper and more effective options to counter a perceived loss in overall security, including the expansion of the highly effective FFDO program and the installed physical secondary barriers (IPSBs) as a supplement to the deficiencies of the hardened cockpit door.4 The focus shifts from protecting airliners to protecting the airports they fly out of, as intelligence shows them to be an increasingly appealing target for terrorists. Using the same cost-benefit analysis techniques used