What Downed Flight 9268?

Though many mysteries still surround the recent crash of a Russian airliner over the Sinai Peninsula, some explanations of what happened are more likely to be true than others. The most probable explanation for the downed plane is either catastrophic mechanical failure or the existence of an explosive device onboard. If a bomb did indeed bring down Flight 9268, the public must maintain a realistic expectation of aviation security efforts and remember that there will always be people who wish to do terrible things to other human beings; occasionally, they will succeed....