Apparently ATA is playing games to get the best deal and yet keep their Pilots happy. The 717 is a well proven and quickly available a/c while the E-190 is relativly new.
As to scheduled service to Europe, why not out of MDW
? I suspect though some of the big boys that ops in O'Hare may object. ATA has plenty of 757's with the reach, they can use the L-1011's they have left for peak times or can go into the used market and find some nice 757's or maybe 767's for that service. (If correct, 757-767 have similar flight decks, so little change for pilots?). With their extensive charter experience, should be no problem as to qualified pilots (maybe the L-1011 pilots can be retrained on 757's-767's?)