At Baltimore/Washington International Thurgood Marshall Airport (BWI), Spirit Airlines is based in Concourse D of Terminal D. What Terminal is Spirit Airlines At BWI? Here are some of the facilities that Terminal D has to offer: retail establishments, restaurants, and cozy seating places. Spirit Airlines customers at BWI should anticipate quick check-in procedures, convenient access to security, and easy boarding gates, all of which contribute to a seamless travel experience. Spirit Airlines offers affordable flights and an easily accessible terminal at BWI, making it an ideal choice for both local and international passengers.