9/11 = Preventable act that instilled fear in people for flying. Maybe not for people on FT, but I'm sure there are many millions of infrequent flyers that had the decision swayed because of it.

Tsunami= Almost unpredictable event that probably doesn't have much impact on peoples' choices to fly. I think people understand that on any given flight, at any given time, there's an inherent risk of an "Act of God" or the like.

While the Tsunami could've wiped out infrastrature or even, sadly, customers for asian airlines, I don't think it really affected the general sentiment of a person's willingness to fly or not. 9/11 definintely did introduce a general reduction in flying, which did not recover to pre-9/11 levels until JUST this past thanksgiving.