I am not sure about swappping US Air to Delta as I don't have a Delta acct. to test it out at the Point's website. I did swap out some Alaskan air points to US air (I think) in the past. I just checked the website but can't find any info on what you can swap and where. I think I remember the exchange rate wasn't that good but I would never use those Alaskan air points again.
I would suggest that you sign up with your miles programs and do a test swap to see what exchange rate you get.
