After the cancellation of nearly 4,000 flights because of the blizzard that shut down all three New York City area airports until late Monday, the backlog of flights is expected to leave hundreds of thousands of passengers grounded for days. Indeed, nearly 1,400 passengers spent Monday night at JFK Airport, according to officials. The next major hurtle for airlines now is to find new flights for passengers since all airlines are flying at capacity already. Ground transportation in the area is slowly returning to normal, though JFK's AirTran is still closed. Buses in the Manhattan area are also limited, but Amtrak and Long Island Rail Road services resumed Tuesday with limited services.