What is religious attire in Islamic context? The djelabba or djelebbiya? Is it the turban or the fez? What constitutes Islamic clothing and what differentiates it from Arab clothing?

I don't think we should mix up male Arab clothing and Islamic clothing. I feel it might only give even more rise to the general concept of "Arab = Muslim", which is not only unfair, but also kind of racist.

The next carefully prepared terrorist attack is not going to be by four guys, cleanly shaven, Western clothes.
I made my own adjustments. I think that any organisation defined as being radically Islamic will take precautions and probably won't go on board wearing a djelabiyya and a turban. Let's not be silly. Maybe that a single Muslim who is sick of the perceived discrimination will cause a scene, but a carefully orchestrated attack? I don't think so.

AQ's promise of retaliation, is some terrorist / Muslim / confused soul getting carried away, trying to make a political statement.
I may presume too much here, but I think al-Qaeda isn't really going to do that much anymore.

Of course, maybe these people on their way to a grand conference on "Islamaphobia" and with CAIR and the national press on speed dial know exactly what they are talking about.
Wait, are you accusing the US press of being pro-Muslim or something? Eh..okay.