The events of 9/11 unleashed a flood of security measures across all dimensions of daily life, many of them aimed at averting repeat attacks on aircraft. So you might imagine that the risks of flying have been much reduced. You’d be wrong, says Arnold Barnett, who has scrutinized the changes in air security regulations, and found them wanting. The cost of another airplane attack, to the airline industry alone, would run around $5 billion. Yet, says Barnett, the government has actually cut four security measures that, according to his cost-benefit analysis, amount to less than the price-tag of a successful terrorist attack: checking photo id’s at airport boarding gates; posing baggage questions to airline passengers; positive bag matches with checked luggage; and a continued ban of U.S. mail on passenger aircraft. While no traveler appreciates delays boarding a plane, and while the minutes of such delays add up to hundreds of millions of dollars per year, citizens would no doubt prefer that all reasonable efforts be made to avoid another tragedy. Relying on airport “sniffer” dogs, computer profiling and better screening devices will not be enough to forestall a terrorist strike, Barnett predicts.