Let me get this straight: the British authorities had been tracking a cell of would-be terrorists for nearly a year, and had appraised the US government of the threat months ago. Furthermore, they have known for some time that the terrorist plot involved the use of liquid explosives, a potential means of attack that was already well known to law enforcement. Pakistan arrests affiliates of the British cell, so the British authorities move in and arrest the locals before they figure out that the jig is up.
Only upon the arrests do transportation officials impose radical new security measures for airline passengers? Why now? Is the threat of attack via liquid explosives suddenly higher now that the active cell working on such an attack has been neutralized? Why not impose these measures months ago when the cell members had not yet been captured and such an attack was thought to be in the offing? I guess I don’t get the point.