Is 911 accident or incident?

[keannu]

I'm not trying to touch a nerve, it might seem a bad example, so if you tell me it's bad, I will delete it.

I learned that accident is something coincidental that you didn't intend, while incident is something intended on purpose by a criminal or an attacker.
So most car accidents are called not car incidents as most of them were not intended. If 911 was intended by the terrorist, then it's called an incident, but from the victims' point of view, as they didn't intend it, it could be called an accident from their position.

If you had an event that is harmful damaging you but that was intended not by you but by the attacker, do you call it accident or incident?

[SoothingDave]

If you are talking about the terrorist attacks on September 11, you are correct. They were not an accident. I am not sure why you think they would be called an accident. The victim of such an attack would not call it an "accident" either.

[Coolfootluke]

I am not a teacher.

When we say "car accident", the word "accident" retains most of its literal meaning. An accident happens, well, by accident, not on purpose.

[Raymott]

If you are talking about the terrorist attacks on September 11, you are correct. They were not an accident. I am not sure why you think they would be called an accident. The victim of such an attack would not call it an "accident" either.

I'm pretty sure they wouldn't call it an incident either. 'Atrocity' might work.
I think keannu has learnt the wrong definition of "incident", which I would normally apply mostly to trivial things. Not every bad thing that happens needs to be classified as either "accident" or "incident".