If you go back to the events of 9/11, one of the factors that I have never thought received much attention is how the hijackers managed to take over the cockpits of the two BOS-LAX flights somewhere over southern VT or upstate NY and manage to find the WTC towers. Or the AA flight that managed turn around and find the Pentagon.

These were not professional pilots who knew how to use the aircraft complex navigation systems. The weather that morning was severe clear and the hijackers may have been able to see landmarks for 50 miles. As an experienced pilot, I can pick out landmarks easily. But infrequent pilots/amateurs can easily get lost even on a severe clear day. And suppose the day was 10 miles visibility in haze... a nice day on the ground, but how would they have found their targets on that kind of day? What if there had been a broken cloud deck?

I would not be surprised at all if the 9/11 hijackers relied on portable GPS receivers to guide them to their targets. To argue that they did this by sight alone, simply by visual reference, strains credulity.

Now as far as I am concerned, the issue was solved by establishing better cockpit security procedures and hardened cockpit doors. But given the fact that the TSA has taken my wine corkscrews and nail clippers in the past, I am surprised that the use of GPS receivers has not attracted more concern.