It is forbidden to create AI aircrafts in native FSX format.
Any developper who would dare to create any native FSX AI aircraft traffic would be immediately banned from all the communities, and his name would be associated with the greatest possible shame, and all the future generations of FS developpers would remember him as "the one who should not be named".
Also, his house would be burnt in flames.
That's the only possible explanation I could find
Honnestly, I have no idea about the real reason behind that. It seems that all FS freeware developpers are refusing to produce any FSX-native models for any FSX AI traffic.
Even the guys at OrbX, who kindly offered some AI traffic for PNW, have used FS9 AI models with props dissappearing in clouds or masking the autogen...
There is ONE package made with FSX-native AI liners, it was a replacement for some WOAI packages, but I never found the courage to install it...