are utilized to support international flights in A-East and A-West during peak times, when no regular gates are available. Variants Passenger Transfer Vehicle (PTV) The Passenger Transfer Vehicle or Passenger Transport Vehicle (PTV) (mobile lounge) is a 54-by-16-foot carriage mounted on a scissor truck, capable of carrying 102 passengers. These vehicles were designed by the Chrysler Corporation in association with the Budd Company, and are sometimes nicknamed "moon buggies" due to their otherworldly appearance. When mobile lounges were first introduced, they had ramps at one end that could be raised or lowered to the floor height of an aircraft. However, after Dulles built the midfield concourses, some of the lounges were retrofitted to be used only for inter-terminal passenger transport. The ramps were removed and doors that could interlock with a terminal building were fitted to either end. Mobile lounges have a driver's cab at each end. The wheels at either end of the lounge can be steered, but the wheels at the end opposite the driver lock into a straight-ahead configuration so that the lounge is steered only by the forward driving wheels. Plane Mate The Plane Mate is an evolutionary variation on the mobile lounge concept. They are similar in appearance to mobile lounges, but can raise themselves on screws (parts of which are contained in a pair of fin-like towers above the vehicles) to "mate" directly with an aircraft. These are used at Dulles and Dorval. This allows passengers to deplane directly aboard and be carried to the main terminal. They are easily identified by the different window configuration. More noticeably, plane mates have two short columns on the roof with yellow beacons mounted on the top, and have an accordion-like canopy at one end (similar to the canopy seen at the end of a jet bridge) and have only one driver's cab and one set of steering wheels at the canopy end. NASA Crew Transport Vehicles Early in the space shuttle program, NASA used the Plane Mate system of mobile lounge to move astronauts directly from the orbiter to crew facilities. A modified vehicle obtained from Baltimore/Washington International Thurgood Marshall Airport in Baltimore, Maryland was used for shuttle landings at Edwards Air Force Base. A similar vehicle was used at the Kennedy Space Center to take astronauts directly from the orbiter to the Operations and Checkout building, where the vehicle was again lifted up for the