Washington Dulles International Airport passengers. Dulles was once assigned the airport code DIA, with each letter corresponding to the initials of Dulles International Airport. However, when handwritten, it was often misread as DCA, the code for nearby Ronald Reagan Washington National Airport. It was later revised to IAD to avoid confusion. The airport's terminal complex consists of a main terminal and two midfield terminal buildings: Concourses A/B and C/D. The entire terminal complex has 123 gates and 16 hardstand locations from which passengers can board or disembark using the airport's plane mate vehicles. Conceived in early planning sessions in 1959, Dulles is one of
Washington Dulles International Airport mezzanine with more room for lines. A new train system, dubbed AeroTrain and developed by Mitsubishi, began in 2010 to transport passengers between the concourses and the main terminal. The system, which uses rubber tires and travels along a fixed underground guideway, is similar to the people mover systems at Singapore Changi Airport, Hartsfield–Jackson Atlanta International Airport, and Denver International Airport. The train is intended to replace the mobile lounges, which many passengers found crowded and inconvenient. The initial phase includes the main terminal station, a permanent Concourse A station, a permanent Concourse B station, a permanent midfield concourse station