I'm experimenting with the AI traffic interface of FSUIPC, and have noticed that sometimes the AI planes will disobey their orders.
So far, I couldn't find out a pattern to this behaviour.
FSUIPC's return codes are being checked and signal that everything's OK, yet the planes will ignore some of their commands.
So far I didn't find a way to check on this other than changes in parameters (speed, heading) after a certain time.
Another phenomenon that I could observe sporadically was that AI planes on approach to a runway (status 'Landing') seem to get erased from the FSUIPC tables once they have been controlled by a third-party program for some time (two or three minutes).
All these phenomena are hard to reproduce since they do happen only from time to time.
PS: I'm using the latest FSUIPC version released March 4th, 2005, and there is no change in this respect to the previous version which I used to develop my piece of software.