I don't agree with the "expert slipping manoeuvre" statement with regard to the second aircraft that hit the WTC.
As you can clearly see from the head-on footage there is a strong crosswind blowing form the aircraft's left to right, this is obvious from the smoke of the first tower.
It looks to me that whoever was flying the aircraft was simply aiming at the tower and not accounting for the drift which would have been obvious from the smoke.
He probably then only realised as he got closer and had to bank the aircraft radically into wind to hit the tower.
If he was even a PPL the chances are that he would have been so mentally overloaded in just flying the aircraft that he probably failed to pick up on the smoke as a clue to the strong drift and didn't notice it until the last minute.
No matter what the case was he unfortunately hit his target with the resulting destruction.
God bless the poor souls who perished in this appalling attack.
[ 12 September 2001: Message edited by: Unusual Attitude ]