WASHINGTON – On Christmas Day, a passenger on a Northwest Airlines flight bound for Detroit tried to blow up the plane with plastic explosives in his underwear. He failed, yet the very attempt shook the U.S. government, set federal agencies against each other and triggered months of political second-guessing. In fact, short of mass casualties, the attack allegedly attempted by Nigerian Umar Farouk Abdulmutallab had exactly the kind of reaction that al-Qaida is after. And, it appears, that lesson is resonating with the terror network’s leadership.