In the same MT gameworld months before 9/11, Asia was "attacked" by bird flu and stock market crash. Demand reduced 30-40% and take 3-5 month to recover. Events like this do happens randomly but they aren't lethal as 9/11.
I'm looking forward for plane event btw (crash, tailstrike, failure etc), which requires aircraft repair. By then, those who cares about aircraft insurance will feel the benefit.