I went to see the movie and kept my eye out for the UFO crashing into the island during the Coney Island scene.  I didn't see shit, and I was looking for it.  The only thing at the lower right of the screen is a cruise ship or some other ocean vessel.  The UFO thing sounds way too speculative.  It should be written out.  For all we know, the film crew unwittingly caught the image of a seagull hitting the water.