A new and permanent C/D concourse (also called "Tier 2") is planned as part of the D2 Dulles Development Project. The new building is to include a three-level structure with 44 airline gates and similar amenities to Concourse B. The concourse plan includes a dedicated mezzanine corridor with moving sidewalks to serve international passengers. The design and construction of the new C/D concourse has not been scheduled. When built, it is planned that both terminals will be connected to the main terminal and other concourses via the AeroTrain. To that extent, the AeroTrain station at Concourse C was built at the location where the future Concourse C/D structure is proposed to be built, and is connected to the existing Concourse C via an underground walkway.