I would prefer to book my travel on United for my upcoming trip, and when going through DTS, the City Pair shows United as the cheapest City Pair, but when you scroll to the "Alternative Option", there are cheaper options on Delta. I'm sure the AO will push me to those.
I am more than willing to pay the difference to fly United, but on DTS it either books into S or Y, and the Y fares are obviously way more expensive. Is it possible to book outside of DTS (so I have access to other fare classes) and still be reimbursed for what the gov't would have spent on my ticket?