As far as I am aware,
If a/c gets a big slot delay, we need to update NAS to stop squawk dropping out.
If a/c is not ready in good time for its eobt, the handling agent must send a delay to IFPS. (or we can do it from the tower if we are not busy and in a good mood!)
BUT as for EFPS, Gonzo, if it is linked into both IFPS and NAS, then I can only assume that when an a/c gets a big slot delay, NAS gets the message and therefore the squawk will not drop out?
In the good 'ol days, I sometimes had to sit in flight plans and type in every slot, SRM, etc etc.
