As someone else mentioned a while back in a similar thread, it would be perhaps an even greater success than OTL of the terrorist attacks if they didn't destroy the towers, but wrecked them so bad they made us tear them down ourselves. What propaganda it would be for the terrorists and other extremists in the Middle East.
And you can't leave the WTC with the scars of plane impacts. You'll get a nice monument out front regarding the people who lost their lives in the attack, and a reconstruction.
Politically, killing 800-1000 people in a terrorist attack will cause basically the same effect as in OTL regarding 9/11.
Well, to be fair, I was a 1 year old when the event happened, and I'm a Brit, so I don't really know that much. I stand corrected.