It would also be technically difficult. There's a 250' difference in elevation between the airport and the Harlem Division at White Plains, 5 miles away, and the intervening terrain is hilly and broken. Kensico Reservoir/Rye Lake occupy what would be the "water level" path to the site. And since that reservoir is part of the NY City water supply, the City DEP would have a big say in any construction in the area.