lots of eyeball information and aerial photos of the area.
Blowing up these tanks would have shut down the airport for months. Would have played havoc w/ travel around the world
http://cryptome.org/jfk-tanks/jfk-tanks.htm
I think his objective was to blow up the entire airport, which would have been more than a few months problem.
Apparently, it would have taken out part of queens as well.