The insurance industry had a bad day on 9/11. Few would imagine a loss of literally everything (the office, the objects, the building and even the people). Of all possibile outcomes, this was the worst of the worst.
What was actually insured from this attack? Was the World Trace Center itself covered by insurance? If I was a business man and brought a place in the building, would I have had insurance?
In the aftermath, what happened? Did the insurance industry pay it all? Did they go broke?
The type of insurance would have differed according to the policy purchased. In a lot of cases, businesses would not have been fully covered. The specifics are usually private between each business and the insurer (often a contractual requirement of the insurer to reduce price table exposure to competitors). What coverage did exist has been disputed by insurance companies.
The insurance loss, while large, was not larger than commonly occurring natural disasters. For 9/11 the direct loss for insurers was approximately $32 billion. Hurricane Katrina was $71 billion. Natural disasters alone cost insurers $20 billion each year.
For more details on 9/11's impact on insurance specifically: Ten Years After 9 11 Property Insurance Lessons Learned.PDF
