Denver International Airport, DIA, is by land size the third largest airport in the world, and the largest in the U.S. It is the 10th busiest airport in the world by passenger traffic with 3 major airlines vying for bragging rights in order of traffic: United (DIA is its 4th largest post-merger hub and was 2nd behind ORD before the merger), Frontier, and Southwest (who only returned in 2005 and is now using DIA as a focus city). In addition, regional Great Lakes Airlines uses DIA as a hub. DIA opened 18 months late on February 28, 1995 amidst great controversy, delays, and cost over runs ($2 billion over budget) principally due to the now abandoned automatic baggage system. Since finally replacing the congested Stapleton, Its unique architecture, user friendliness, and 6 runways have made it a passenger favorite and operationally efficient airport in the face of the tough weather in the Denver area. DIA is located far east of the city in a sparsely populated area in the Front Plains. The airport has a midfield configuration similar to Atlanta Hartsfield. Landside operations are located in the Jeppesen Terminal, named after aviation safety pioneer Elrey Jeppesen. The terminal is separated into west and east terminals for passenger drop off and pickup. The airport's iconic white tensile fiberglass roof is aesthetically designed to be reminiscent of the snow-capped Rocky Mountains in winter. The central security and shopping area is bathed in natural light, but ironically the ticketing areas themselves are dark and low ceilinged. The central area of the airport houses two security screening areas as well as a large fountain and exits from the underground train system. The north side of the Jeppesen Terminal contains a third security screening area and a segregated immigration and customs area. Passengers are routed first to airline ticket counters or kiosks for checking in. Since all gates at Denver are in the midfied concourses, passengers must pass through any one of the three separate security screening areas for admittance into the secure air side of the airport (one at each end of the main terminal, with escalators down to the trains, plus one at the end of the walkway to Concourse A). After leaving the main terminal via the train or pedestrian bridge so called Lorenzo's Bridge, passengers can access 95 full-service gates on 3 separate concourses (A, B, & C), plus gates for regional flights. There is a new $600 million terminal under construction adjacent to the current Jeppesen Terminal that will house a railway station that will link DIA to downtown Denver and hotel by 2016. Concourse A has 37 Gates and is used by all international airlines and international arrivals. It is used by British Airways, Aeromexico, Air Canada, and Lufthansa. Denver is one of the busiest airports worldwide with only limited international operations. Frontier, DIA's #2 carrier, American, AirTran, Alaska, and JetBlue operate from here as well. It is connected to the main terminal by a bridge called "Lorenzo's Bridge" which though rarely used as such can accomodate an airplane up to A320 size underneath. It is so named as Continental was a hub carrier at Stapleton and insisted on the close end Concourse A at DIA. Instead CO closed its hub with the move to DIA. Concourse B has 77 gates and is exclusively used by United and its merger partner, Continental and current Star Alliance member, US Airways. Concourse B is the longest concourse at DIA. Further afield is Concourse C with 22 gates. Southwest, DIA's #3 carrier, is the main occupant here but Delta and Delta Connection operate from here as well. There are plans available to expand Concourses A & C as well as build new Concourses D & E should traffic require it.