The engines throttled down after they ran out of fuel, this happens quite a bit.
OK folks you are right and I am wrong and explosives also blew down the WTC. There is plenty of documentation on that.
That is not what I wrote why are you trying to obfuscate?
Boeing's engineers claim (we both can believe or disbelieve them) that as soon as communications to their 747 engines are loss they immediately go to a default idle mode. They said this believe it or not.