Apologies being late with this post.
I remember 9/11 like yesterday. I walked into the office to be told that the Twin Towers had been brought down with thousands of deaths. I felt physically sick and cannot even imagine the fear and terror of those passengers and those in the Twin Towers.
There was a repeat on TV recently of one aircraft flying into the second tower, to quote a US Army padre during the Korean war (after finding murdered US troops), "They have the faces of men, but the minds of animals."