You do pose an interesting and difficult scenario for terrorism. Terrorism isn't just the bangs but the fear of the bangs as well. If Terrorists can frequently challenge the security system with enough false positives they can drive up the costs and reduce the effectiveness of the monitoring system.
A spate of false positive hits in airports simultaneoulsy would paralyze the air traffic system for days. I wouldn't want to fly during a high alert period. I'm sure that both the terrorists and counterterrorists have red teamed this scenario in theory already.
So....If we get hit hard and FR gets knocked off the air...how will we know what is going on?