I do agree that the pesky "some" sounds ominous.

It's difficult to compare costs based on the publicly released numbers because [as I learned here on FT a few weeks back] those CASM numbers are raw and not stage-length adjusted. So even after it meat-hooks its costs, US Air will have a high-looking CASM compared to most because it flies shorter hops ("stage lengths" in airline jargon). So unless two airlines have a similar distribution (both average and range) of segment lengths, comparing CASM's is not really telling the story.