Diesel8,
taking your time? - Don't forget that they were internal US flights that were hikacked. In the US you treat Domestic and International travel in totally different fashions. International travel is subjected to high security, whilst Domestic is subjected to minimal.
I have witnessed passengers baggage loaded onto a Domestic flight, and the passenger fail to join the flight due to a ticket problem. The a/c left witout the pasenger, but with her baggage. Now that isDomestic travel in hte US. Wouldn't happen in Europe.
Very shortly, by the end of next year, ALL checked in baggage will be X-rayed. no plans for that in the US.