To the unfamiliar, catching a glimpse of these strange vehicles shuttling around the airport can be quite surreal, like something from an old sci-fi movie.

The airport “mobile lounge” was indeed a futuristic concept when the Washington Dulles International Airport opened in the early 1960s. Today, they are a dying breed.

A cross between an airport gate lounge and a bus, the unusual vehicles were used to provide a waiting area for passengers and then transfer them to boarding ramp.

A slightly later development, the “Plane Mates,” with their distinctive fin-like structures on top, cut out the ramp entirely. The Plane Mate lounges could be raised and lowered significantly—by screw lift devices housed inside the fins—allowing the mobile room to line up with the aircraft door.

With the advent of the air bridge, airports suspended these transportation innovations. But at Dulles, they are still used to transfer passengers between the older concourses. The doors of the lounges match up with doors on the side of the terminal buildings, allowing passengers to easily get on and off these retro “buses.”

However this role, too, is gradually being taken over by a rail system, and these odd-looking vehicles will eventually be phased out of service altogether. A number of excess Plane Mates now appear to be parked around the Dulles airport, possibly having been mothballed.

Hopefully, some will be preserved as part of aviation history. In the meantime, if you are passing through Dulles you may be lucky enough to use one, or at least catch a look.

Plane Mates and mobile lounges are also still in use at Montréal–Pierre Elliott Trudeau International Airport, and mobile lounges have previously been used in a limited number of other airports, including Paris CDG (up to the 1990s), New York City, Mexico City Airport (up to 2007), and Jeddah (until the early 2000s).  Plane Mates are a necessity at the Baltimore-Washington International (BWI) US Air Force Air Mobility Command (AMC) terminal to board the “Combi” aircraft that carry military personnel and cargo to such exotic places as Thule, Greenland.  Versions of the mobile lounge were also used as crew transfer vehicles by NASA.