New York's airspace is the busiest in the United States and one of the world's busiest air transportation corridors. The three busiest airports in the New York metropolitan area include John F. Kennedy International Airport, Newark Liberty International Airport, and LaGuardia Airport; 109 million travelers used these three airports in 2012, and the city's airspace is the busiest in the nation. JFK and Newark Liberty were the busiest and fourth busiest U.S. gateways for international air passengers, respectively, in 2012; as of 2011, JFK was the busiest airport for international passengers in North America. Plans have advanced to expand passenger volume at a fourth airport, Stewart International Airport near Newburgh, New York, by the Port Authority of New York and New Jersey. Plans were announced in July 2015 to entirely rebuild LaGuardia Airport in a multibillion-dollar project to replace its aging facilities.