alt Hacker NewsThere's a pretty strong trend in that timeline of two types of "bombings":
(1) Bombings in which the bomb is supplied by someone who isn't flying on the plane;
(2) Failed hijackings in which there was no intent to bomb the plane, but a bomb accidentally went off.
also, people always immediately think of terrorism, but TIL that life insurance policies are responsible for way more plane bombings than I thought