Denver International Airport (IATA: DEN, ICAO: KDEN, FAA LID: DEN), often referred to as DIA, is an airport in Denver, Colorado. By land size, at 53 square miles (140 km2), it is the largest international airport in the United States, and the third largest international airport in the world after King Fahd International Airport and Montréal-Mirabel International Airport. Runway 16R/34L is the longest public use runway in the United States. From January to September 2011, Denver International Airport was the 10th-busiest airport in the world by passenger traffic with 39,953,117 passengers.
Denver International Airport is the main hub for low-cost carrier Frontier Airlines and commuter carrier Great Lakes Airlines. It is also the fourth-largest hub for United Airlines. The airport is a focus city for Southwest Airlines. Since commencing service to Denver in January 2006, Southwest has added over 40 destinations, making Denver its fastest-growing market. Denver International Airport is the only airport in the United States to have designed and implemented an ISO 14001-certified environmental management system that covers the entire airport.
The airport's distinctive white Teflon-coated fiberglass roof is aesthetically designed to be reminiscent of the snow-capped Rocky Mountains in winter. The catenary steel Cable system, similar to the Brooklyn Bridge design, supports the roof. DIA is also known for a pedestrian bridge connecting the terminal to Concourse A that allows travelers to view planes taxiing directly underneath and provides sweeping views of the Rocky Mountains to the West and the high plains to the East.