Reply #16: I guess one would have to know more about the investigation to know

[fishwax]

according to the official line (or at least, what I heard on the news), british authorities were gathering a great deal of info from the investigation, but had to cut it off suddenly because they came to believe that the executuion of the attack might be imminent. I have no idea the truth of that.

But it does make sense that the longer one keeps the investigation open, the more information they can get (and the more useful that information might be), not just about a specific plot but about the organization and the structure behind the plot. Sending out a warning to flyers would also send a warning to plotters and to the rest of that organization/structure. Also, we don't really want authorities flooding our circuits with warnings every time they begin an investigation--we've gotten enough false alarms over the last five years as it is.