I guess we would really need to know what flight OP is on to JFK, since delta offers a mashup of mainline and regional flights on that route, as well as both C gates and B gates (at Terminal 4). So if the flight comes into a B gate, it's just a matter of a short (or lengthy) walk. I flew in from SLC last week, got off the plane, exited the jetway, and crossed the hall to the opposite gate to wait for my international departure. A plane coming in at the C gates would require the Jitney shuttle as others have said. However, keep in mind that if that's the case, 1 hour might not be enough, as it can take 20-30 mins to wait for/ride the shuttle between terminals. I would be concerned, with the propensity for delays between those two saturated airports.