AI aircraft are deleted by FS if they do not move for five min, unless you have one of the addons which modifies the time to make it longer.
Follow Stuart's advice. Also check to see if the parking spot which the aircraft was assigned to might be disconnected from the rest of the taxiway system. Look also for runway links which are broken into different segments. Some people do that to make large aircraft clear the runway faster. That often results in small aircraft not clearing the runway at all.
Rwy 35R can be a problem at LIMC because traffic on 35L can make the AI control system stop aircraft from taxi until 35L is clear. It is best to have a diamond system so that AI aircraft will cross 17R/35L without stopping for aircraft on the runway. That might be your issue also.
Another possibility is that if the person who did your AFCAD "fixed" the taxiway designators, he would have broken/ destroyed the default taxi path segments. This will cause aircraft on the ground to hold for aircraft which taxi half the airport away. Something we did not fully understand when AFCAD came out so it is not in the AFCAD manual. The only way to fix that is to start over with the default airport and build the AFCAD again - without changing taxiway designators. Taxiway E appears critical in the LIMC default AFCAD. It must be in three segments so the aircraft will not be stopped by aircraft taxi on Taxiway C or Rwy 17R/35L.
Last edited by ReggieF5421; 01-31-2010 at 10:28 AM.
@ PawPaw's house - near KADS, Addison, Texas, USA