<P> All non-United flights operate out of these two concourses as well as some United Express flights . Concourse A (which has 47 gates) composes the eastern part of the closest midfield terminal building . It consists of a permanent ground level set of gates designed for small planes and regional jets used by United Express, and several former Concourse B gates . The concourse is primarily used for international flights . Air France operates an airline lounge opposite gate A22, Etihad Airways operates a First and Business Class lounge across from gate A15, and Virgin Atlantic has a Clubhouse lounge across from gate A32 . Concourse A's AeroTrain station is located about halfway through the concourse, between gates A6 and A14 . </P> <P> Concourse B (which has 28 gates) composes the western half of the building . It is the first of the permanent elevated midfield concourses . Originally constructed in 1998 and designed by Skidmore, Owings & Merrill and Hellmuth, Obata and Kassabaum, the B concourse contained 20 gates . In 2003, 4 additional gates were added to concourse B, followed by a 15-gate expansion in 2008 . In addition to the AeroTrain station located between gates B51 and B62, Concourse B also has an underground walkway to connect it to the main terminal . Concourse B is used by some international carriers, and is also utilized by all non-United domestic and Canada flights . The facility also includes a British Airways Galleries lounge, a Lufthansa lounge divided into Senator and Business class sections located between gates B49 and B51, and a Turkish Airlines Lounge near gate B43 . </P> <P> Concourses C / D are solely used for United Airlines flights . All mainline United flights and most United Express regional jet operations operate out of these concourses (some United Express flights use Concourse A). </P> <P> These concourses were constructed in 1983 and designed by Hellmuth, Obata and Kassabaum . The two concourses have 22 gates each, numbered C1 - C28 and D1 - D32, with odd - numbered gates on the north side of the building and even numbered gates on the south side . Concourse C composes the eastern half of the terminal and Concourse D composes the gates on the west half of the terminal . The C / D concourses were given a face lift in 2006 which included light fixture upgrades, new paint finishes, new ceiling grids and tiles, heating and air conditioning replacement, and complete restroom renovations . </P>

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