Can someone explain to me the different between Y and B class in United? The FAQ states that B has "minimal restrictions", but I can't figure out what these are. In my (admittedly limited) experience with domestic flights, Y and B class seem to have comparable fares (generally around $1700 from SFO to JFK or IAD). So then wouldn't Y always be better since you get higher priority for upgrades?

Next question is how you can actually purchase a Y-class ticket on the united.com web site. I've tried selecting "economy (no restrictions)" and/or "Miles-YB" on the web site, but this doesn't work reliably. Sometimes I get Y, sometimes B, sometimes even another class like M (which is too bad if I'm hoping for a free upgrade).

I even called united and asked about this several times. One representative told me United doesn't sell Y-class tickets any more, except the day of the flight. I didn't believe her, so I called back and got someone else who sent me over to technical support who told me there's a bug in the web site. Surely it can't be the case that Y tickets are this hard to buy, can it? I must be missing something.

Thanks.