They claim their effectiveness is amplified by the Deterrent Multiplier Factor. If there are ANY FAMs flying on a particular day, anywhere in the world, they can take credit for deterring 100% of the attacks, since those under-staffed terrorist cells can't afford to send (let's say) 0.5% more teams to compensate for the FAM-protected flights.

Of course, we know they can, if they were going to, send two extra team members, the first one to smoke out a FAM, then the other N-1 terrorists would sit back and watch a second team member smoke out a possible second FAM, then the final team of N-2 terrorists would attack the reinforced cockpit door and fail because it's really the cockpit doors and pilot procedures to not come out that are the real deterrent.