Assuming the hijackers had some training and/or advanced knowlege of the 757/767, would it not be prudent for the FAA to perhaps ground all 57s/67s for a few extra days while they further their investigation?
I know this would be devastating to some carriers that rely on these types quite heavily, though more hulls/lives lost would be an even greater concern. Some carriers, like Southwest, Alaskan, or Northwest would feel little effect.