While it's likely the missile if it runs out of fuel won't likely hit land if launched from near JFK airport, you forget that the water surface has the consistency of concrete when the missile hits the water at several hundred miles per hour. That would be enough to cause the impact fuse to detonate, and somebody out in Jamaica Bay would have hear the impact.
"...somebody out in Jamaica Bay would have hear the impact."
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So what???
Nobody was interested when a few of my friend saw the explosion on Flt. 587 before it gyrated, started to break-up and eventually nose dived into the Rockaway Penninsular. They were near the sea plane ramps at Floyd Bennet Field and the explosion was almost directly overhead.