Kip Hawley used to be the head of the TSA, from 2005 until 2009. He is publicizing his new book about security in America's transportation systems, and wrote this for the Wall Street Journal:
More than a decade after 9/11, it is a national embarrassment that our airport security system remains so hopelessly bureaucratic and disconnected from the people whom it is meant to protect. Preventing terrorist attacks on air travel demands flexibility and the constant reassessment of threats. It also demands strong public support, which the current system has plainly failed to achieve.
The crux of the problem, as I learned in my years at the helm, is our wrongheaded approach to risk. In attempting to eliminate all risk from flying, we have made air travel an unending nightmare for U.S. passengers and visitors from overseas, while at the same time creating a security system that is brittle where it needs to be supple.
He goes on to discuss what needs to change for air travel safety to become sustainable. Excellent points, including his commentary about why those changes haven't happened yet.