In checking my reservations this morning, I found that my January 20th flight from IAH-DFW had been changed from a CRJ-700 to an ERJ145. Since this is the last leg on a long, international trip, and I had successfully UGed with miles, I looked for options. All flights before 4:58 PM to both DFW and DAL are ERJ145s. I looked around for other days to move up or back my date of travel, but every day I checked was the same. I checked December 19th, and there was one CRJ200, but nothing with an F cabin until after 5:00 PM. Nov. 18th has a couple of E170s in the afternoon, but no mainline at all. It looks like UA is further reducing their already poor options between Houston and Dallas on this very heavily traveled route. It makes connecting in or originating from IAH very unappealing. By comparison, AA has many flights throughout the day IAH-DFW, all mainline. As a very frequent traveler through IAH to DFW/DAL, this is a major downgrade in service. It means that most of my trips to/from Dallas will usually end and start with the worst of the RJs. How could their analysis of this route be so vastly different from the competition? It's sure not enhancing the value of being a loyal MileagePlus flyer.