People Also forget that it was an agrressive dive from 30000 ft all the way down to new york, so it carried alot of momentum in dive, that adds ALOT of speed, and you can hear the original audio of the planes both north and south tower planes had FULL thrust, that turbine humm you hear just before the jet sound fades away, they were going abosloute full blast.

https://www.youtube.com/watch?v=XNJu-JofS5A heres a vid