Regardless of the threat, from the would-be bombers’ perspective, the explosives and planes were merely tactics. Their goal was to cause terror, and in that they’ve succeeded.
Imagine for a moment what would have happened if they had blown up 10 planes. There would be canceled flights, chaos at airports, bans on carry-on luggage, world leaders talking tough new security measures, political posturing and all sorts of false alarms as jittery people panicked. To a lesser degree, that’s basically what’s happening right now.