stopped an ambitious al qaeda plot to blow up a passenger jet bound for the united states. a u.s. counter terrorism official tells cnn the explosive device is similar to the one used by the would-be underwear bomber. just like that bomb, there one did not contain metal, which raises real questions about whether it could have gotten passed airport security. as of yet, the person who had developed that bomb had not yet bought a ticket. here s defense secretary, leon panetta. what this incident makes clear is that this country has to continue to remain vigilant against those that would seek to attack this country and we will do everything necessary to keep america safe. fran townsend is cnn s national security contributor, a member of both the dhs and cia external advisory boards. chad sweet is a former dhs and cia official, also the cofounder of the chertoff group, a global security firm. good to see both of you. fran, i know you ve been reporting on this throughout the day