I just fast-traveled to some farm outside Solitude. A dragon appeared.

But it didn't attack. Why? Because it was already dead.

Yeah, and I'm not talking about a skeleton of a dragon I previously slayed that hasn't respawned yet. No, he just dropped dead on his own accord, and I was able to loot his body and everything.

Weird.

I had this happen when discovering Meeko's Shack. I had just walked inside when I heard a dragon overhead. When I went outside it literally just "fell" out of the sky, dying on impact.

I bet it died from fall damage while attempting to land. What I mean is the ai wanted to land, but changed what it wanted to do but couldn't change from the landing, got confused trying to decide which script to follow, and in the mean time it hit the ground dying, ending the process of trying to choose which script to follow.

Any number of other things I guess could explain it, but that's what I reasoned out of it. I have not seen this happen yet.

There are occasions when I used to fast-travel and random dragon skeletons would just appear where I showed up (a dragon skeleton in Riverwood, Solitude, etc.).

But I've never had a Dragon literally just fall out of the sky and die in front of me.