According to what I've seen on CNN and CBS, it was a hijacked American Airllines plane that hit the WTC.

All airlines have been closed.

Apparently, there are only 30 floors left of the south tower after it collapsed about 10 minutes ago.

What kind of hate would drive terrorists to kill so many innocent people? I guess that is what terrorism is all about. People doing terrible things because they can't find ethical ways to solve their problems.