AP, 11 March 2010: 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.

For the first time, the group that carried out the Sept. 11 attacks and has prided itself on its ideological purism seems to be eyeing a more pragmatic and arguably more dangerous shift in tactics. The emerging message appears to be: Big successes are great, but sometimes simply trying can be just as good.

U.S. officials and counterterrorism experts say the airline attack and last November’s shooting at Fort Hood, Texas, prove that simple, well-played smaller attacks against the United States also can be harmful to the American psyche, although not as devastating as a 9/11-style attack.

In a recent Internet posting, U.S.-born al-Qaida spokesman Adam Gadahn made a public pitch for such smaller, single acts of jihad. “Even apparently unsuccessful attacks on Western mass transportation systems can bring major cities to a halt, cost the enemy billions and send his corporations into bankruptcy,” Gadahn said in a video released and translated by U.S.-based Site Intelligence Group, which monitors Islamic militant message traffic.

It’s a message that officials believe has been evolving for the last year and has turned upside down the prevailing wisdom that the next al-Qaida attack against the U.S. must be bigger and bolder than the one on Sept. 11, 2001. . . . .