ISRAEL ENACTED NEW US REGULATIONS MONTHS AGO/updates
Why the last hour? Because that is the only way terrorists can insure that their terrorist act will be perceived as such. There is no point in blowing up an airplane if no one needs to acknowledge they did it.
Even as is, Al Qaeda happily takes credit for the close call. It had successfully refocus attention on it's own ability to outsmart American authorities and undermine the airline industry. What a terrific recruiting tool for the British radical Imams whose students, at least 25 in number, are at this very moment busy training in similar ways to get to heaven.
In other words, this partial Al Qaeda victory could have been and should have been avoided.
Update: I wrote too hastily - We are back to normal until next time - We all know there is going to be one!
Update 2: A reader pointed out that additional efforts to prevent the blowing up of a plane in the final hour may also be motivated by the wish to limit damage on the ground.