Originally Posted by Santos Dumont

Mesa, Republic and SkyWest are the only 3 E-Jet operators for United. All of the 3 have a sizable fleet of the type, but SkyWest and Republic have a few more of these birds than Mesa does right now.

Last time I checked, SkyWest E-175s don't touch IAH. Republic has had a small hub there ever since Continental and United merged, though they refuse to open a pilot domicile to go with their operation there... All of Mesa 48 E-175s are based at IAH.