On a recent trip through Stansted, I happened to get a position at the
front of the little transit train on the way to Satellite 2 so I whipped
out my pocket camera and took a few pictures.

https://www.flickr.com/photos/recliner/sets/72157668434701408

While waiting for the delayed flight in the Satellite, I realised that the
long underground transit ride had actualy brought us back to a satellite
pier that's also connected directly to the terminal building with a
walkway. I was, of course, aware that the underground route has a long
curve, but hadn't realised that it takes you almost back to where you
started. It's certainly an unusual route for an airport satellite pier
shuttle, and the convulated route seems to be based on the original plan
for another satellite pier where the cargo terminal now stands.

Stansted has one passenger terminal with three satellite piers as well as a
nearby freight terminal. All passenger gates are on the satellites, not the
main terminal building. The three satellites are each connected to the
terminal in a different way:

- Starting at the north east, Satellite 3 is used by international flights
using gates 40-59. It's connected to the righthand corner of the terminal
by an up-down dog-leg passage, used by all passengers. The transit is not
used. I think this spartan satellite is used exclusively by Ryanair.

- The centre Satellite 2 is used by both domestic (gates 81-88) and
international (gates 20-39) flights. The domestic gates are closest to the
terminal, and passengers access the terminal using a straight, direct
overhead walkway, not the transit. But the international gates further
along the satellite are accessed by the underground transit which follows a
long J-shaped route to get there.

- The southwest Satellite is remote from the terminal. Its international
gates 1-19 can be accessed only via the transit.

- The cargo terminal is further to the southwest. It doesn't have a transit
station, but perhaps surprisingly, the transit passes underneath it, and
could easily have a station had another passenger satellite been built
there.


So, when you set off from the terminal, you descend into the tunnel,
heading southwest, passing just underneath the walkway to Satellite 2. As
you enter the tunnel portal, you're just passing the end of Satellite 1
(but can't see it).

The tunnel then continues straight for some distance, taking you under the
southern end of the cargo terminal. It then has a long 180 degree bend,
after which you pass back under the cargo terminal, heading northeast. This
is where there could have been a station had another (fourth) passenger
satellite been built, as BAA originally intended.

The line continues underground, under Apron A, heading northeast, until you
get to the station under Satellite 1. It then continues in a straight line
under Apron B, to Satellite 2, the final station. At this point, almost two
miles after you started on the transit journey, you're within 150m of the
starting station at the terminal. You could have walked it quicker!

The transit then crosses over to the other tunnel, and retraces its journey
for arriving passengers, again taking them on a two mile journey to cover
the direct distance of about 150m to the arrivals station at the terminal
(which is just along from the departures station).

This map (from Wikipedia) makes it clearer:
https://www.flickr.com/photos/recliner/sets/72157668434701408

Stansted is running at well below its runway capacity. If it ever grows to
need more passenger terminal capacity, it will simply need a new, fourth
satellite replacing the current cargo terminal, with a station on the
transit line running directly underneath. There's plenty of room to move
the cargo handling area to the west, or north of the runway.