AI aircraft models are often aircraft models that were re used so they are normally not at ground level as is ; some of them were pushed a bit in the up direction, some have a z offset in their xml animation file, and others even have an offset in the AI traffic files.
Note that today AI models that have an offset in the AI traffic files can not be used of AI scenario for example.

Since I'm actually working a bit on AI aircraft animations, I propose to not use the offset tag in the AI traffic files (ie doing as if that offset was null) and to update all the AI models (or their xml file) that need to be updated (that must be like 20 models that need to be updated, 18 are already correct as is).

AC folder     Model name     ground level ?
717     717.ac         yes
737     B737-300.ac     no
        B737-300.ac     no
747-400     747-AI.ac     no
757     B757.ac         no
        757-200         yes
767     767.ac         nearly
777     777-300.ac     yes
        777-200.ac     yes
        777.ac         nearly
A310     A310.ac             yes
A319     A319.ac             yes
A320     a320-fb.ac     yes
A321     A321.ac             yes
A322     a322.ac             no
A332     A330-200.ac             no
A333     A330-300.ac             no
A343     A340-300.ac             no
A345     A340-500.ac             no
A346     A340-600.ac             no
A380     A380.ac                 yes
ATR42     atr42.ac             no
Bae146-200     bae146-200.ac     yes
beech-200     beech-200.ac     yes
Bombardier-Challenger     chal604.ac     no
CRJ-200     crj200.ac             no
Dash8     dash8-400-remap.ac     yes
        dash8-300-remap.ac     yes
DH7     dh7.ac                 no
Embraer-Legacy     legacy.ac     yes
ERJ145     ERJ-145.ac         yes
erj195     erj195.ac         no
Fokker-50     fokker50.ac     no
Fokker-70     fokker70.ac     no
Fokker-100     fokker100.ac     no
MD80     md-80.ac             yes
MD90     md-90.ac             yes
saab-340     Saab-340.ac     yes

Your thoughts ?