Air transports do work in TS's demo, and I think they work in vanilla TS. Somewhere along the line of patches, the logic got broken.
The most common way is to use the
Carryall=yes tagAlso give a look at the air transport's
paratrooper logicIMO it's better to make it a flying vehicle (like in RA2), which will enable rotors, shp ability, turrets, and a lot of other things.
this topic covers the pros and cons, and the best way on how to go about it.