To answer part of your question, republic has multiple crew bases that fly for multiple code shares. Its always been that way. Regarding the direct competition, no one really knows. You can bet all the code share partners knew about this midwest/frontier thing beforehand. Maybe there were agreements, maybe there weren't. Consideing delta nearly owned midwest, im sure they are just fine with what happened. Midwest/Frontier don't really compete with US Air. So the only real question mark is United. Guess we'll see what happens there.