I just can't understand how people think about these things. If I had gone to all the trouble of planting a bomb on a plane -- a very difficult task, I assume! -- why in the world would I write a note telling people that it was there? Wouldn't I want the plane to take off with my bomb on board? And if someone else wrote the note, why wouldn't they just tell people in person about the bomb? Why communicate so strangely?
The right answer is really just to ignore these nonsensical notes. Too bad nobody will do that.
Bruce