Come September 13, United Airlines will offer two nonstops a day between Charlotte and Denver (DEN). This is a route that United has flown before, mostly recently in 2008. There is a significant difference between then and now: When they last flew CLT-DEN, it was on Boeing 737s that seated about 125. This time it will be on 76-seat Embrear E175 regional jets that seat 76. CLT-DEN is a long route for a regional jet, though the Embrear 175s are pretty comfortable and do have a first-class section. United is also resuming Raleigh – Denver flights, also twice a day on Embrear E175s, on Sept.13.