I was just listening to NPR and heard that the President had been appraised of the plot against the airways and was monitoring the situation from his ranch in Crawford. Since the British deemed the threat serious enough to ban liquids and carry on luggage from UK flights and seriously mess up travel, I think it prudent to hear more information before passing judgement on the extent of the threat.
However, after getting being caught on vacation at his ranch when the Presidential Daily Briefing was presented that indicated Osama Bin Laden was determined to attack in the US (and blowing off the warning according to the book the "One Percent Doctrine"), after sitting stupified in front of a room of school children on 9-11, and after playing guitar at a shindig when Katrina was about to innundate the Gulf Coast, how could the President possibly stay on vacation in the face of another serious threat?
Modern communication makes it possible to be on top of a situation anywhere in the world, but when my country is threatened and if I had the responsibility, I would be in DC. Furthermore, I would be looking for a feint.