A paper in the latest issue of the Journal of Law and Economics demonstrates the welfare cost of more stringent security at US airports.
The Impact of Post 9/11 Airport Security Measures on the Demand for Air Travel
Garrick Blalock, Vrinda Kadiyali & Daniel H. Simon
We examine the impact of post-9/11 airport security measures on air travel in the U.S. Using five years of data on passenger volume, we evaluate the effects of the implementation of baggage screening and the federalization of passenger screening on the demand for air travel. These two congressionally mandated measures are the most visible changes in airport security following the 9/11 attacks. Exploiting the phased introduction of security measures across airports, we find that baggage screening reduced passenger volume by about five percent on all flights, and by about eight percent on flights departing from the nations fifty busiest airports. In contrast, federalizing passenger screening had little effect on passenger volume. We provide evidence that the reduction in demand was an unintended consequence of baggage screening and not the result of contemporaneous price changes, airport-specific shocks, or other factors. Moreover, this decline in air travel has substantial welfare implications. Back-of-the-envelope calculations indicate that the airline industry lost about $1.1 billion, a tenth of the projected revenue lost because of 9/11 itself. Similar calculations show that the substitution of driving for flying by those seeking to avoid security inconvenience likely led to over 100 road fatalities.
Ungated version here. Of course, more stringent security also has benefits, since it helps deter terrorist attacks. But my guess is that politicians tend to over-regulate in this area, since their reputations suffer more harm from a terrorist attack than they gain from streamlining airports.