The RW side seems to be fairly safe - if anything, mainline is using the 170s to fill up the holes in their patchwork schedules. Seeing as RAH owns as much stock in US Air as they do, I would assume RAH/CHQ are relatively safe. I'd be only slightly more worried about PSA, but Comair has shown us all that being wholly owned by mainline != get out of jail free card. Piedmont is filling their niche too well to run into any real problems. Anyone else is fair game.