Thanks to Amanda for forwarding along this article from the National Review which sheds some more light on the situation on NW 327. It appears the band was accompanying Nour Mehan[n]a, a Syrian artist.

The remainder of the article goes on to state that he thinks the original author was right to be worried and that especially due to a warning that had been posted for June 29th, it was a bit disconcerting that the airline officials weren't more vigilant.

In the end, it appears this was an innocent situation where band members were meeting up in Detroit and then headed to a gig in southern California.