If people are not "allowed" to capitalize off 9/11 then every tv news broadcast, newspaper, and journalist who had anything to do with coverage of the story since that date 5 years ago should be condemend and hung.
As was stated, this movie was heavily supported by the families of those on the flight..and the movie is no different at all than any news station, talk show, etc. that does any sort of coverage on the event. It's simply in a different form, but the idea is the same--to capture a moment in history in a way that people will watch, and help remember. The real people that exploit this event are the people that use it to push their personal, selfish agendas to either slam the US and its policies..a la the Michael Moores of the world..or the people that use the tragic event to further his political agendas and wars that he may have questionably started.
Personally, I remember that day when I was in school (senior in HS), and most people honestly did not care at all for what happened, and 90%+ of us treated the day like any other day. Only a handful of teachers around the school seemed to change the plan that day, but otherwise you really couldn't tell that that day was any different than anything else.