He said al Qaeda's new emphasis on training Westerners to in turn provide terrorist instruction in the West reflected the group's looser control over plots than just a few years ago.

Unlike the 7/7 bombers, and other recent terrorist conspiracies like a plot to attack Manchester in 2009, the Birmingham plotters do not appear to have been in touch with their handlers in Pakistan after returning to the United Kingdom.

Pantucci says the pressures on al Qaeda have resulted in a shift toward a new model of "fire and forget."

The March 2012 Toulouse terrorist shootings provided further evidence of looser control by al Qaeda of terrorist plots in the West. The perpetrator of the attack -- Mohammed Merah -- was encouraged by the group to return to France to launch an attack during a short stay in the tribal areas of Pakistan in September 2011 but planned every aspect of the operation himself, including which targets to strike.