the OP could get lucky with the current continuous pricing trial and it might still go through.

Wait so you're saying that even though I would save on my ticket I may pay for my family member because of the letter code changing?

Ok. Here is another idea but I think it's going to cost more. I have enough points to get 2 PP tickets there. But the way home when I do 1 way PP is just as expensive as a RT ticket for 2. Which I don't understand. Is there a way to do all miles one way and MUA on the way back without booking one-way tickets?

Thanks again.

It’s a possibility, yes. The “letter code” is a representation of inventory, but inventory doesn’t work the way that it works at a retailer. UA inventory is fungible, because, once you’re on the plane, all the seats are the same. Inventory can be updated at any time, and, in fact, UA has a process that will go through and compare the number of tickets sold with historical trends and their internal projections, and may then adjust inventory either up or down. The precise timing of these inventory scans is a trade secret, but observationally, one time that they appear to happen is whenever a ticket is sold for any particular flight.

Inventory on your return flight is somewhat constrained (or, was yesterday, anyway; I didn’t go back to look today). It was showing O9 A2 R0. That means, UA was willing to sell at least 9 more tickets in Premium Plus — you’ll never see the numbers go above 9 — but only 2 in the A fare bucket, and 0 in the deepest discount R fare bucket. If you were to buy a ticket, it would use the A fare bucket, but it would also trigger UA’s computers to adjust the inventory. They might just adjust it to O9 A1 R0 or O8 A1 R0. However, they could easily adjust it to O9 A0 R0 or O8 A0 R0 — that is, they could say “sure, this morning we were willing to sell a pair of seats in A class, but now that we’ve sold one, our sales trends look better than expected, so let’s hold off on selling a second one and see if we can sell O fares instead.

I can’t say with any certainty what will happen, but this is a very real phenomenon that I’ve seen personally.

Unfortunately, there is no way to combine them the way that you want. And, the reason that the PlusPoints award on the way back is more expensive is the same as the root cause of the pricing concern I have — PE inventory is limited on the return, so they’ve raised prices.

Note that you’ll face the same possibility of purchasing one ticket affecting the other if you try to do one RT mileage ticket and one RT MUA ticket.