Originally Posted by UA-NYC

It might be worth calling to try and swap your mileage UG for the SWUs. Or , worst case, keep watching, and if you see the R space open up, cancel and re-UG with SWUs.

Yes, 1K better than CO Plat on UA. And yes, you can change it after the first flight. You have 6 days in-between which is perfect, as 1K window is 100 hours.