I'm booking SDF-DCA-BOS on 10/22 then with United as a codeshare with USAirways BOS-DCA-SDF on 10/24 also with a United codeshare with USAirways. All legs will be operated by USAirways, so will I be checking in at the United desks or the USAirways desks? I don't think I've ever booked a codeshare flight before. For some reason this option is quite a bit more expensive if you book through the US site.
Flt. numbers are United 3862 and United 2704 then United 2831 and 3627.