I anyhow have the feeling that physics die with the ai pilot. Offline you kill the pilot and the plane just flies on.

Perhaps they have implemented different levels of FM according to the status of the plane:

Level 1 (most accurate FM): pilot seat is occupied by player
Level 2 (less accurate FM): AI is sitting there
Level 3 (even lesser accurate FM): Pilot bailed out
Level 4 (UFO or perpetuum mobile - whatever you like): dead AI pilot occupies pilot seat.