Boarding an aircraft is a process that we are all familiar with, whether it is done via a jetbridge or external stairs from the apron. For the latter method, passengers are often required to take a bus transfer to a remote stand, where boarding via stairs occurs. However, another method of boarding an aircraft exists, known as mobile lounges.
These little-known vehicles serve as something of a halfway house between jetbridges and stairs, but they fell out of fashion decades ago. That said, you can still find them at a select few airports. A product of the 1960s The 1960s were an exciting time when it came to innovation in the world of aviation.
For example, this was the decade when the legendary Anglo-French supersonic jetliner Concorde made its first flight (although it didn't enter service until the 1970s). But back on the ground, further innovation was occurring. This came in the form of mobile lounges, which first entered service at Washington Dulles International Airport (IAD) in 1962.
As seen in the photograph below, these vehicles are much like the transfer buses that we know and love (to hate) today, but they can be raised and connected to an aircraft like a jetbridge. This meant that passengers boarding aircraft at remote stands didn't have to be exposed to the elements, letting them walk straight onto the aircraft much like a jetbridge. The concept was cooked up by Finnish-American architect Eero Saarinen, who wanted to make life easier for passengers when shuttling.