They wouldnt happen to be an MD-83, Piper Cherokee and a deHavilland dash 8, would they?
These aircraft are default AI, and they dont show up in FS, if you dont have any additional traffic installed then I wouldnt suggest deleteing them, as you would be flying in an empty sky, you can, however, download free AI to install. Just go here
http://www.projectai.comAlso, I wouldnt worry so much about it, they dont take up much space, if you dont want the fake airlines in your sim just rename your AI traffic .bgl. Anyway, what are you trying to do in FSEdit?
Cheers,
Alex