Originally Posted by
Gonzo
It's not so much for the next flight, as transponders are filtered out from being displayed on the ground radar when the target is on stand. It's so that we see the aircraft registration on the radar if the aircraft is towed from one stand to another. Ground handling procedures say that the towing crew must tow with the transponder on.
Can't you see the registration if the aircraft has the code from the previous flight(I suppose another aircraft could be flying with that old code).