Transport/air transport networks

In several guides I see advice given along the lines of "Form a transport network/ air transport train to increase your range".
I was wondering if anyone has any tips as to how to do this/ screenshots of their transport networks? I don't understand how I can move large numbers of units without needing excessive numbers of air transports.

N.B. I'm not including in this the trick of moving 6 tanks/marines with one air transport by using their own movement.

Thanks

The pics don't explain it very well, you have to have a transport right at the edge of the other transports range then drag the units into the new transport you created, do not join the two transports or it will join their ranges together. Though this is useful in some situations like when you have two full transports or with ground units, boosting one stack with one ahead of it.