I used to work security at government licensed nuclear plants. The utilities put out millions and in the end those measure really didn't make facilities safer. It wasn't the public who was the problem, it was employees. Screening all potential employees for psychological problems before hiring prevented problems from developing. For it is the insider working at a facility who is actually the biggest threat to safety.
In the case of airports, who is it we are fearful will kill us? Our fellow travelers. And of course you've realized that the airlines are having a wretched time financially since 9-11. Few people, yours truly included, want to fly nowadays. It's impossible to screen travelers carefully and thoroughly in a timely manner and still not bankrupt the airlines.
Exactly! And all this is further proof that preventing 9/11 was virtually impossible. If ANY President had told the American public before 9/11, for example, that all air travel will be suspended until we can increase security?--what would have been the response by the public? Even if the public had accepted this, the president would have then been blamed for creating an economic disaster for the airlines and all travel-related business.
The present system of airline security is only an interim solution, implemented knee jerk style in the aftermath of 9-11. Technology solutions are comming online pretty quickly, and promise to put most of those white shirt TSA employees back to work at McDonalds. Thanks to Richard Reid with his TriAcetone-TriPeroxide shoes, we will all have to put up with the shoe searches for a few more years. The current explosive detection technology misses this substance entirely, but sensors are under development.