There are numerous problems, the biggest is that the larger airports are constantly under pressure to push more and more people through in less time. Automated systems help, but have limitations. The average bags can have absolutely anything in them, frequently including tools, machine parts, anything a worker need to carry to their next destination. For a bag that is alerted by automatic systems a screener could have around 30 seconds to make a decision, before the next bag arrives. Sometimes, hopefully rarely, mistakes are made. I had a similar discussion with the Chicago folks, their point was that this got through, my point was the scope of the battlefield tourism problem in Belgium and France, and, how many items you think get caught at the European airports? Is this 1:10? 1:100? 1:1000?
