John F Kennedy Intl (JFK) in New York, NY.
Where to walk your dog:
Some of the passenger terminals have greenswards (external areas where there are trees, plants and grass). If you are lucky enough to be at one of those terminals, you can relieve your dog there, otherwise the street at the front of the terminal is the only option.
American Airlines has a pet relief area on the departure level of its terminal at JFK airport. The area is 30 X 50 foot and has grass, a walkway, two benches, a red fire hydrant, and a Mutt Mitt dispenser.