Before I could transfer miles back and forth, I booked a trip on UA using CO miles. I got first class on the international segment but could only get coach on the domestic segment.

All segments are on UA metal although I noticed they booked them all on CO code share flight numbers. The agent told me that they could not waitlist UA flights for first at the time.

Has anyone found a way to waitlist the first class set on UA metal when the miles used are CO miles?

Thanks for your help.