The area has two major airports, Ronald Reagan Washington National Airport and Washington Dulles International Airport. While flights from the older National Airport (a hub for American Airlines) are restricted for distance, frequency, and flight paths due to the proximity to federal facilities, Dulles is the region's second busiest airport in both passenger loadings and aircraft movements, and the sixteenth-busiest airport in the United States by takeoffs and landings in 2007. Dulles is the region's primary international gateway, serves as a hub for United Airlines, and has recently improved its low-cost carrier offerings with the addition of multiple flights by Southwest and JetBlue.