Northern Virginia from the older National Airport (a focus city 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. Commuters are served by the Washington Metro subway and the Virginia Railway Express, a
Washington Dulles International Airport Eero Saarinen, and it is highly regarded for its graceful beauty, suggestive of flight. In the 1990s, the main terminal at Dulles was reconfigured to allow more space between the front of the building and the ticket counters. Additions at both ends of the main terminal more than doubled the structure's length. The original terminal at Taiwan Taoyuan International Airport in Taoyuan, Taiwan was modeled after the Saarinen terminal at Dulles. The design included a landscaped man-made lake to collect rainwater, a low-rise hotel, and a row of office buildings along the north side of the main parking lot. The