Osama bin Laden and his gang of thugs have declared war on the U.S. His people almost invariably fit the profile.
Uscit, seems like we already have plenty of seething hatred within our borders without all the scary foreigners. Let me guess, you wish me dead for being such a traitor to your America for standing up for people WHO HAD NOTHING TO DO WITH THIS.
I see your point, but how do we decide of whom we will demand proof of citizenship? Then, after requiring that citizens carry proof with them before boarding, won't terrorists find ways to counterfeit that documentation?
IMO, we need to look for other means, but the next attacks won't involve commercial airliners anyway because simple non-intrusive measures -- like skymarshals -- will prevent it.
Your proposal IMO is an example of "fighting the last war." Now we will need to increase our security procedures to defeat bombings and bio/chem assaults.