So I know there are already many threads about the woes of PNR splitting... but my situation is somewhat complicated and I want to make sure I'm understanding the lay of the land correctly.

I have a roundtrip booked for 4 individuals, including myself. I'm 1k, but none of my companions are Premier. I've requested PlusPoints upgrades for all 4 pax on both outward & return. After putting in those requests, I opted to split into 2 PNRs of 2 pax each to increase the likelihood of upgrades clearing as pairs. Right now we are in slots 1-4 for the outbound flight with a few seats open, a couple days from the flight, so I think odds are good for the airport list but bad for the advance list. The return flight, on the other hand, has a ton of inventory and I like our odds there.

I understand that with instruments applied, the PNRs will automatically split again at check-in. I'm less concerned about loss of Premier benefits (i.e. luggage, boarding), but I want to make sure I don't impact our upgrade chances for the return flight. If our PNRs are split, am I correct in understanding that the other 3 travelers will no longer be next to me on the return upgrade list, but will rather drop to the bottom of the 1k section of the list? If that's the case, given odds of all 4 upgrading are good for the return, I'm thinking I should cancel my requests for the outbound and mark for no upgrades (even though an upgrade looks likely for the airport waitlist). Am I interpreting this correctly? Any thoughts/suggestions?

Welcome to FT. When you use +Ps the impact will be minimal in my experience when it comes to split PNRs. There is still an effect in the priority within the +Ps waitlists, but on the grand scheme of things you are still ahead of everybody hoping for a comp upgrade

Interesting... So you're saying that if I let the PNR split, the likely result is that on the return flight, my companions would drop to the bottom of the 1k P+ section, but still be above the 1k mileage upgrades, and all the other premier tiers?

There is no difference between mileage or PlusPoints priority. CPU is a lower priority.

While for years the companions lost the elite's status on the return after an outbound PNR split, reports for the past year suggestion it is now maintained.

Interesting... I've also heard that the companions can be assigned the lowest possible fare class on the return when the reservation splits. Or does that not apply when instruments are attached?

That is true for off-PNR CPU, not supported upgrades (PlusPoints, Miles)

Note also the OP keeps referring to companionS, however specifically mentions that they split the reservation immediately after applying the instruments "to increase the likelihood of upgrades clearing." (So essentially created a PNR of OP + 1 companion.) WineCountry, perhaps you can provide anecdotal experience but wouldn't the OP's splitting of the initial reservation into 2 + 2 cause the two non-status passengers to lose the 1K upgrade priority, or does the fact that an instrument transaction simply took place while all four passengers were on the same initial PNR with "ghost" 1K status cause the 1K priority to become embedded in the instrument upgrade request and maintain after the split. I do not have experience with instruments but with the CPU, where I was traveling with a companion and I split the reservation after the CPU window (and the PNR showed the "CPU requested" icon) but before check-in and my non-status companion went on the Upgrade Standby List (and even ended up getting upgraded at the airport), which tells me that after the computer flipped the "CPU requested" switch that computer coding for my status became embedded in my companion's individual ticket and exclusive of mine. My assumption is that had I split the PNR prior to the upgrade window the outcome would have been different because there was no transaction to trigger attaching my status to my companion's ticket.

SAP

I can confirm that my initial split reservation did not negatively impact my companions' placement on the upgrade list. In fact, amusingly, the PNR with the two non-Premier members is actually ranked higher than the PNR I am on! Worth noting is that the UA agent left two companions on the original PNR but split myself and one companion onto a new PNR with a new confirmation code. My best guess is that the other PNR is ranked higher based on time of request, as the new PNR is considered to have a later request time (i.e. the time of the split).

Just another update here... I decided to withdraw the P+ request for the outbound flight only on the PNR that doesn't include me. Called UA to do this, but the agent misunderstood and removed the instrument from both outbound *and* return by mistake.

When I added it back to the return flight, I figured it would mean this other PNR would now be ranked below mine. But in fact, it returned to its exact prior position ahead of me in line! (All factors are equal, including fare class.) All I can think of is that it's still going off of time of request, and that when you cancel and then reinstate a request it sticks to the initial timestamp.

If the upgrades don't clear in advance, I'll test this theory at T-24 by checking in my reservation first to see if it jumps ahead.

On a trip last September, I had to split my wife (no status) from my PNR at check in for outbound for CPU purpose. She was ahead of me on upgrade list for both outbound and return. In fact, my wife cleared upgrade on return flight while I was #1 when the flight took off. Go figure.

It's been a while, but my recollection from splitting is that if you initiate the split you tend to get the new PNR, meaning the companion keeps the first-in-time priority based on original booking date.

I can confirm that exactly this happened to me a couple weeks ago. I had a 4 pax reservation that I split into two pairs; my pair got a new confirmation code while the other pair retained the original, and was placed higher on the list.

Interestingly, neither PNR was further split at check-in for either flight. Is this phenomenon dead?

don�t know about instruments per say, but as a premier who has been at all levels below 1K since the merger in different years, I�ve noticed companions don�t always show up right after me - sometimes there are a few names between. It�s my hypothesis that while the wording of the companion benefit for upgrades insinuates that companions should be right below the status traveler, the system is programmed to put them at the bottom of the list for that status. In years my wife and I have been gold, for example, our non-status kid has been a couple of names below us, but above others. It�s just strange.

As for the split itself, I concur with the opinion that has improved over the years - non-status (or lower status) companions definitely didn�t always inherit the highest status on the original PNR after splitting, it definitely changed some time ago (at least up until the pandemic - I don�t have experience flying since March of last year).

Generally this is cleared up by looking at who is on the original PNR and ticket number (which is lower). A lot depends on the how the original ticket was structured and how the PNR gets split and how the ticket numbers are assigned and when time stamped for the waitlist. That are things we don't have control over and therefore appear mysterious.