Folks,

I'm sure this is probably answered somewhere, but, I've been searching for about the last 30 minutes and can't figure it out. "XN" being too short to search on doesn't help .

I am looking at BDL-LAS in E when I notice that for not much more miles, I can book F. But when choosing seats, F is not an option for the second leg. When I look further, I see that 2nd leg will be "United Economy (XN)". See picture. So, what gives? What is the point of a booking option like this?