The other problem with these through flights is their upgrade scheme. There is a glitch in the upgrade process. If you're not upgraded on the first leg of a through flight, you are taken off the upgrade list for the second flight. This affected me from an AUS-DEN-SAN flight a couple of months ago. I was aware it had happened, and mentioned it to the people in the United Club, and a red coat at the gate. A passenger of lesser status was upgraded ahead of me. The United personnel said they were aware of this glitch but powerless to fix it. I never heard back as to why.