Whipper snapper,
Prior to 9/11 skymarshals (all 10 of them) were restricted to international flights. That is where the threat was perceived because of all the TWA/PANAM hijackings. Furthermore, if a domestic aircraft had been hijacked, it would not have had the fuel on board to cross the atlantic so it would have had to land somewhere in the USA to get fuel first where its tires would have been shot out. That was felt to be enough of a solution because nobody had the forsite to realize that hijacking the aircraft would be the first step in using them as a weapon.
But since they were looking to use airplanes as weapons and a flight headed to athens would have had MUCH more fuel on board and therefore would have been a better weapon, the evidence is that skymarshals did work. They went for the flights with out them...
Terrorists took advantage of the different levels of security in America. That doesn't exist anymore.
Interestingly if you do actually ban armed guards from your airplanes, think how nice it will be for the US airlines. They will get to carry Tony Blair and his onterage, or Prince Charles or anyone else who brings armed security with them on the plane. Boy that will go over well
Cheers
Wino