Christmas days attempted bombing of the Delta Airlines flight brought the beast of terrorism and terrorist activity back into the international spotlight, spreading fear and pandemonium around the world. I doubt that anyone has been comfortable flying since.
I think that the root cause of terrorism is Belief. Terrorists believe in their philosophy or ideology so strongly that they will do almost anything to carry it out, to see the objective of their beliefs fulfilled.
My essay, “On Belief” describes this further. I invite you to read it.