One occurrence or Two? Well, it's mixed news for Larry Silverstein. The Second Circuit has held that the terrorist attack on the World Trade Center on 9/11 was one occurrence for certain insurers bound under the so-called Will-Prop form, but upheld the jury verdict finding that, for purposes of other insurers not bound by that form, the attack constituted two occurrences. This may warrant further discussion after I've had a chance to read it in full. It's a long one, over 70 pages.
The decision in SR International Business Insurance Co. v. World Trade Center Properties can be found here.