I have over the past decade been in and out of HESH hundreds of times. Security was merely an act of going through the motions and ticking the boxes. I have little reason to believe that anything has changed.
On that basis, I am incredulous as to why a terrorist act has been ruled out with such vigor. In light of the I.S. claim to having brought down the aircraft, my incredulity remains.
Note : I am NOT saying this is the result of a terrorist act, I am merely saying it cant be ruled out YET.