So far the reports say that there’s one passenger plane, allegedly a Boeing 767 from Boston, and another smaller plane. President Bush stated that this probably is a terrorist act. There are speculations about one or both of the planes being hijacked. A Palestinean group called DLFP has, according to rumors taken responsebility for the actions.
Here’s a link to a video recording of the second plane smashing into the world trade center: http://www.nrk.no/rammstein?id=139010&aid=1281666