Transportation Security Administration is responsible for administrating the security through the United States. However, they aren't making our airports safer. It's just a show put on to make passengers feel safer.
Someone tries to light his shoe on fire, so they start checking for shoe bombs. In fact they make Mr and Mrs Smithers from Iowa take off their shoes, because the very act of forcing Mr and Mrs Smithers to take off their shoes reinforces the idea that the serious shoe bomb threat is being properly checked for and prevented. We can rest safe.
A few months later, someone demonstrates a 2 part liquid bomb, so after the fact, they write a new regulations that disallows liquids on board.
I could show you how two widely available household chemical powders that could detonate a 747 in midair. I can also assure you that DHS isn't checking for them, because they are so common that both are already part of most people's luggage. DHS won't do anything about such a threat, until someone actually DOES it.
You see, we are REACTIVE. Some does X - so we start to look for X. Thats not the way to approach security. We need to stop beng reactive. We need to think in terms of potential threats and contingencies.
For example, you basically have to assume that weapons can and will get on board airplanes. There is essentially no feasible way to prevent a half way intelligent hijacker from smuggling the kinds of weapons that the 9/11 terrorists used - on an airplane - in the current day with the current security measures. Any child could get a boxcutter onto an airliner. So, you've got to be prepared for that.
You should also assume that an attacker is going to know enough about chemistry to bring an unconventional explosive, so you've got to talk to chemists. Find out what exothermic reactions could occur on a plane, not just conventional explosives - any powerful exothermic reaction - invent dozens of ways that a chemist with reasonable knowledge could destroy an airplane, and then work through how to prevent it. Then - start talking to the biochemists - find out about all the organic agents and toxins that could be used to kill everyone onboard an aircraft.
For ID security, we should at least electronically verify the ticket at every stage of entry into the airport, and biometric id is really a crucial step. Until we have a biometric system, its impossible to guarantee that John Smith is really John Smith even if he has John Smith's ID.
Finally, I don't know this for a fact - but I strongly suspect - the DHS computer system and FBI computer system are both hopelessly antiquated. Otherwise, I wouldn't have to answer questions about my criminal background and whether or not I have lived in Concord, California when going through US Customs. I have a very common name, unfortunately, and someone who shares my name is apparently not a nice guy.
Personally, I don't feel safe flying, because I know that the security is just for show. However, the world is an inherently dangerous place. I still fly. It doesn't keep me up at night that such dangers are possible, because I know they are very unlikely. However - maybe it should keep SOMEONE up at night.
PS - This article is a reprint with some minor editing of an article that I wrote six monthes ago.