It is very hard to find ai packs for regional/metro airlines such as american eagle, continental express, delta connection, etc. Mainly because there's just so many of those flights that it gets quite daunting to program all those flightplans. Some advice I can give to you is to look for ai packs under the names of those regional operators such as expressJet, Pinnacle, Mesa, Chataqua.
Hope this helps.
Just a sample of my personal art.