This one reeks...having the #3,4 and 5 carriers in a code share deal is bad for competition. CO and NW would often undercut DL on spot specials for routes like ATL-SLC. In a code share they could continue to cut capacity and make the fortress hubs even less competitive. ATL thankfully has AirTran (though not Southwest), but AirTran's route system is still relatively small (like a heavier version of ComAir). DL also would add fliers but not routes to most of Asia and might even try to get the others to go along with insULT.