By the 1980s the original design, featuring mobile lounges to meet each plane, was no longer well-suited to Dulles' role as a hub airport. Instead, midfield concourses were added to allow passengers to walk between connecting flights without visiting the main terminal. Mobile lounges were still used for international flights and to transport passengers between the midfield concourses and the main terminal. A tunnel (consisting of a passenger walkway and moving sidewalks) which links the main terminal and Concourse B was opened in 2004. The Metropolitan Washington Airports Authority (MWAA) began a renovation program for the airport including a new security mezzanine with more room for lines.