I am based in the SF Bay Area and so almost always fly United. I'm flying to New York on USAir (via Las Vegas) and want to use my US Div Miles number on the short hop to LAS while keeping my United number on the rest of the flights. (The idea is to keep my USAir miles alive...) It was the best available fare for my last minute travel and I was curious to see what kind of in-flight power USAir has since SeatGuru claims that the A319 has inseat power in economy on USAir.

I remember many years back (pre-merger) I had no trouble doing things like this whenever I was flying USAir, but this time the nice agent on the telephone told me that it was impossible to change a frequent flyer number on only one segment of an itinerary. I'd rather keep the bulk of the EQMs on United.

Has something changed? Is there a way around this?

I tried the search function but did not find anything. My apologies if this is a FAQ.