It's been big news this holiday season, the new TSA full-body scanners... but it doesn't matter. What people fail to realize is that none of it matters in the least. In any arms race, one team must always be one step behind the other.
First, it was guns and knives, so we instituted the metal detectors. Then plastic explosives worn under the clothes, so we have full-body scanners and "puffers" (the trace element detectors that use mass spectrometry to identify chemicals that have been blown from your person into the detector with puffs of air). But what's next? There is no end to it, and anyone who stops to think about it will see that.
The scanners and puffers are useless against explosives carried internally (and let's face it, if somebody really wants to blow up a plane, then swallowing a chunk of C4 is not out of the question), and no detection method can stop something taking place outside of the secure area (think of O'Hare - the doors to the passenger drop-off lane are literally 50 feet from security lines, with dozens of people in them). Additionally, there's always a way to sneak something past security using any number of loopholes. Consider, for instance, that not all of the air cargo is scanned before being loaded onto the same plane that you've just boarded (though new rules make it required). What of the tons of products that are brought into the airport each day by the restaurants, booksellers and vendors? One bottle of Coke out of a pallet could be filled with explosives, just waiting for the person who knows to buy it from the machine. And all of this neglects the "easy" stuff, the mistakes and errors and judgment calls and weather and engineering failures that give rise to many more air accidents than terrorism.
My point is not to give people ideas (as the joke goes, sexual harassment training is the best place to learn new sexual harassment techniques), but to say simply that nothing is safe. That's just the way it is. That's life. Flying's not safe, driving's not safe, the train isn't safe and even staying at home isn't safe. The level of danger is, of course, relative; statistically, you're more likely to be in a car accident than a plane crash, or to slip in the shower than be struck by lightening. But the basic truth of the universe is that nothing is certain. Nothing.