<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by Steve M:
Well, the same thing that's done to ensure you don't sit next to a "KNOWN AND WANTED CRIMINAL" aboard a long-haul or city bus, in a movie theater, at a play, in the next cubicle at work, behind you in line at the grocery store, or in any number of other situations.</font>
At the same time, your can be reasonable reassured that you nuclear plant operator, your police-person, your airline (and non-airline) pilot, even (in most states) your bus driver, and lots of other people in positions of doing lots of damage to society are screened for not being "KNOWN AND WANTED CRIMINAL".
I think it's clear now that airline passengers are in a position to do enormous harm to people -- 3 buildings and (luckily "only") 5,000 deaths are harm enough -- yet the standards are the same as those of being a spectator at a play.