What's unusual is acts of war and terrorism are standard exclusions in insurance policies. Silverstein had these exclusions written out (due to the 1991 atttack) and for the premiums 3.5 bil in coverage generates, the insurers were too greedy to walk away. It's a contract and definition dispute. The bombing example is very interesting. Multiple planes dispatched by one entity on one plan. But multiple strikes. An angle to consider is that the single occurrence theory assumes that the two strikes must have been committed by the same group under the same conspiracy. I know, odds are a trillion to one that it was two and coincidental.
Wrong jailhouse punk. You forgot how to count. If your loss is $250 an occurrence, that's all you collect per occurence, even if you are covered for more. In your example, there is a total loss of $500. Insurance, btw, covers against loss. Please refer to my first post in this thread.