Originally Posted by LAX UA 1K
In my experience the Chicken lets you substitute a more valuable instrument but not a less valuable one. If you used a confirmed instrument, it won't let you change to 500 milers. But if you requested with 500 milers, you can substitute a confirmed instrument. At least that is what I recall.
Charles
I believe it depends on when your upgrade cleared. If you were able to confirm the upgrade at the time of booking with a CR1 that's what you'll be required to use. But if you were waitlisted for the upgrade and didn't clear until the day of flight, you can choose to use 500 milers. At least that has been my experience.