Originally Posted by
Often1
If there's better SFO-DEN service for OP on AA or DL, that would be the way to go.
Bet there are a lot of direct flights with AA and DL from SFO to DEN and esp with 757 or bigger planes... IIRC only Frontier (other than UA) has direct flights from SFO to DEN and DL has exclusively CRJs to DEN through SLC, while AA mixes an occasional MD-80 through DFW.
Good luck finding better airline than UA for that route, but Frontier might be it, if you like A319s and don't mind that level of service...