But the 9/11 culprits were not familiar, were not American, were not used to identifying the same landmarks from years of flying the same airline out of the same airports. To someone like that, one freeway looks like another, one river looks like another, and Nashville, Louisville and Cincy would all look the same, more or less, medium large cities on a big river.

And just picture the view out your side window on a hazy, humid day with 7 to 10 mile visibility, broken cumulus clouds etc. Was America just unlucky on the morning of 9/11/01 that there were no clouds, visibility unlimited? Some of you may recall that the evening of 9/10/01 was quite stormy over the Northeast corridor with numerous thunderstorms.

Whether or not GPS receivers aided the 9/11 terrorists in carrying out their flights to destruction, we cannot know. AA 11 could have followed the Hudson River, but both AA 77 (the Pentagon plane) and UA 93 both flew more or less straight lines towards DC. But given the fact that the TSA fears onboard nail files and corkscrews, I remain surprised that they have never been concerned about a device that could potentially allow hijackers to fly directly to a pre-programmed target.

Keep in mind, I am not personally advocating the ban of GPS receivers or their use aboard airliners. I think the root solution to 9/11 was better screening, hardened cockpit doors and wholesale revision in the "rules of engagement" with hijackers.