Thank you everyone.
BOAC - I have seen the very thing many years ago in Brussells of all places. I always wondered (doh!) how the driver would fit under`the aircraft without banging his head and alway thought that it would be hell of a noisy and dangerous for someone to be under a moving aeroplane!! How stupid am I?
However, your post certainly clarifies things. Interesting, referring to the Brussels thingies, I only ever saw them using it on a Boeing 737. I never`saw it used on an Airbus or a Bae 146 / Avro RJ, which were the predominant types using the terminal that I used to fly from.
Is this underneath tug not suited to other types and only B737, or was I just witnessing this out of coincidence.
MANy thanks to all of you again. Very enlightening.