runway 12–30. If this runway is built, the current runway will be re-designated as 12L-30R while the new runway will be designated 12R-30L. An expansion of the B concourse, used by many low-cost airlines as well as international arrivals, has been completed, and the building housing Concourses C and D will eventually be knocked down to make room for a more ergonomic building. Because Concourses C and D are temporary concourses, the only way to get to those concourses is via moving walkway from the Concourse C station which is built in the location of the future gates and Concourse D by mobile lounge from the main terminal. In the short term, United Airlines has constructed a buildout on Concourse C between gate C18 and the AeroTrain entrance for use as a Polaris Lounge for international passengers. Further expansion plans include a new three-story south concourse building above the AeroTrain station for Concourse C, to replace Concourse A regional gates built in 1999. Decades-old rules set by Congress that limit the number of takeoffs and landings, as well as distance of routes, at Reagan Airport were intended in part to keep more flights at Dulles. However, those rules have been weakened by Congress over the years, causing Dulles to lose 200,000 passengers to Reagan between 2011 and 2013. In 2022, it was reported that Dulles would include the largest airport-based solar and battery development in the U.S. as part of an agreement with Dominion Energy. The solar panels would cover more than on land and would be sufficient to provide energy to more than 37,000 Northern Virginia homes during peak production. Meaning of IAD Dulles originally used airport code DIA, the initials of Dulles International Airport. When handwritten, it was often misread as DCA, the code for Washington National Airport, so in 1968 Dulles's code was changed to IAD. Terminals The airport's terminal complex consists of a main terminal (which includes four of the original gates, "Z" gates), and two parallel midfield terminal buildings: Concourses A/B and C/D. The entire terminal complex has 139 total gates: 123 gates with jetways and 16 hardstand locations from which passengers can board or disembark using the airport's plane mate vehicles. Inter-terminal transportation Conceived in early planning sessions in 1959, Dulles is one of a few remaining airports to utilize mobile lounges (also known as "plane mates" or "people movers"), now only used for