A bomb with a barometric trigger would be more likely. It could be set to go off a few thousand feet above ground level, this ensuring the plane would go down in a populated area.
Except that a takeoff from JFK would be a very poor choice, if that is your intention. Rockaway is such a narrow peninsula that it was just extremely bad luck that this plane hit a populated area. Rockaway is surrounded by lots of water, and the chances would have been extremely high that the plane would go into the water.
By the way, while I get this post in, let me ask a couple of other questions. Is Wall Street open today? Has there been activity in put options for American Airlines in recent days?