I ended up in a WIN-WIN-WIN situation! I finished a business/vacation trip and was ready to fly RNO(Reno)-LAX-ORD. I was told that UA's flight RNO-LAX was cancelled. They booked me on AA RNO-ORD, which was quicker.

But I thought I might want to spend one more night in Reno (not a bad place), and get my UA miles.

As I approached the desk, I heard an elderly woman complain that she HAD to get to Chgo for a funeral the next day. She was starting to go ballistic. I signalled the desk agent, and suggested that I'd be willing to spend a night in Reno, let the woman take my AA seat, and I'd take a UA flight the next day.

The agent jumped on my offer, the woman calmed down & was appreciative, and I had nice night in Reno.

Bonus: the agent upgraded me from coach to 1st class. I got my RNO-LAX-ORD miles plus a 50% ? bonus, and several hours of champagne!