I work in probably the safest area. If we assume that the rag-heads want to inflict maximum casualties, they will either set bombs to go off in the most crowded areas - check-in and the plane itself. If they did develop a bomb invisible to the various scanners to get on a plane, it would be set to detonate when the plane is in the air - long after it has passed under our boots. They want a bigger prize than a few lowly baggage handlers.