D-ALPA used to have some very good analysis of Delta's overlap with other carriers as they worked to predict the effect of various mergers. That data would be equally useful to quickly determine the overlap with United and Continental's tie up. ACL pointed out some of the areas, like Cleveland which might not survive consolidation.

However, it is my opinion we've all been getting a bit of a free ride as a result of United's mismanagement. If United was run by Continental (which is assumed would be the result) then they would be a much more viable competitor.

US Air will likely be broken up, or merged in parts. In the mean time I see them as kind of a supercharged Spirit. An airline that makes little sense, other than the fact their costs are so incredibly low that they bounce along in ground effect.