Exactly, grateful to have experienced this a couple of times on BA but certainly not something I expect nor an event that occurs often. I was surprised to see on this AA flight a full PE and nearly full Y with a relatively empty J and so figured I might have increased chances of an opup than usual if Oneworld elites were treated similarly to AA elites.

I do realise that, thank you :). And certainly at no point I hope did I imply that I expected an opup to be anywhere near likely, just inquiring as to what extent my Oneworld status would increase my small chances.

For an upgrade from PE to Biz, your options are:
* Upfare: call and pay the difference to change your fare in advance (it is usually expensive)
* SWU / Points + $$ upgrade: while you might not have an SWU, if you have AA points/miles, you can get on a waitlist for an upgrade that would be a similar category. For your flight it will be 25,000 + $350
* App / Online upgrade offers: when you pull up your PNR in the AA App or online, you'll often (but not always) be given options to upgrade for a fee. It is sometimes reasonable, often not, and the offers can change (hourly/daily). So if you don't like today's, wait and see what comes tomorrow.
* At check-in (counter or lounge): if there are seats left in business, they will often sell them for a fee at check-in. Again, sometimes these are reasonable, sometimes not.

While I'm sure it is possible to get an op-up, I certainly wouldn't count on it.

I've had just a few op-up experiences in my years of flying. The most noteworthy was on JL SGN-NRT. I was a lowly AA Plat, and had booked a rock-bottom fare (about $600, AUS-DFW-NRT-SGN). Somehow JL needed my seat in coach, and the agent apologized to me as they handed me a boarding pass for business when I checked in. I really should have bought a lottery ticket after that.

Not sure what is the pecking order for Opups.
For international upgrades, it is elite status first, then rolling LPs.
If Opups use the same criteria and assuming you get grouped with AA EXPs, you probably have 0 LPs (as you accrue BA Avios/Tier Points), so at best, you would be last among ALL AA's CKs and EXPs.

P.S. My one and only opup with any airline was an upgrade from business to first on AA FRA-DFW (when it existed). I had no status back then.

*IF* AA takes OneWorld status behind its equivalent tier, then OP would be after the PPros, because they are also OneWorld Emerald :)

Plotting a strategy to maximize your chances of an op-up on a specific flight is likely to be about as fruitful as plotting your strategy to win the Powerball. In over 50 years of flying I have received two op-ups. One was on Eastern Airlines from NY to Florida in 1988, and that was not related to status, as there was no such thing back then. I have no idea why I was chosen. And the other was on a BA LIN-LHR flight in 2015, when my wife and I got bumped up to CE. That was certainly related to my OWE status. I still remember the full English we got, but then the food always seems better when you get an unexpected upgrade.

Anecdotal evidence is not in any way a statement of rules but as a BA Gold I have never been upgraded on an AA flight. This encompasses ten years of flying 4-8 segments a year on AA in a mix of Econ (US domestic) and PE & Biz (transatlantic). Which is fine, since I would expect to be after all AA elites and there are a huge amount of those.
Besides the occasional BA PE to Club World, I've been operationally upgraded once on Lufthansa In all my years of flying them and a few times on Austrian as an Asiana *G.
My best streak was on Air France in 2004, the year they introduced Platinum elite status (top of three tiers) and made all AF Rouge elites (top of two tiers) platinum. I was upgraded on six out of eight transatlantic segments from economy to biz on my flights that year, which was truly amazing.

I have been op-up'd twice as a BA Gold on AA. Neither seemed elite heavy though: JFK-SJU and SAT-ORD. TATL is most likely a whole 'nother thing.

I've been op-up'd twice flying as an AA EXP. Once when I was flying SFO-JFK; I received a complimentary upgrade at T-100 from Y-J and then, upon boarding, was op-up'd to F. J was oversold and AA moved me and a CK up to F, even though we had been previously upgraded to J for free.

The second time was DFW-GRU. I'd scored a very cheap Y-PE in-app upgrade for around $175-$200. Upgraded to PE (Y-J was like $3,500). When I went to board, the machine spit out a J pass. Obviously I didn't complain and I didn't see anyone waitlisting an SWU. The Agent told me that PE was oversold and that it paid to be at the top of the AA elite list. Another passenger I guess saw me board and went up to me after in the Business Cabin. He told me he was EXP and also got bumped to J. We were shocked since it was a 787-9 with limited J seats (compared to the 777-300ER).

In my situation I'm unsure whether there were also OWE considered for op-ups. But I can say that the Gate Agents will absolutely prioritize AA elites over BAEC Gold. Why would anyone reasonably think otherwise? And when you check in, if there's anyone waiting on the upgrade list trying to use an SWU, you're toast as they would obviously get priority over a non AA elite not using an upgrade instrument. What about in-app upgrades? Any good deals?

I would say about 1% chance, but for a day flight PE should be fine and not worth any extra costs. (Unless you have an expiring BA upgrade instrument that works here and that will go to waste otherwise).

- You have a better luck with AA than me! Out of my continuous ca. 15 years as EXP, I was never op-upped by AA. Moreover, on one of the transpacific flights out of LAX we were at the top of the upgrade list with SWU pending but GAs upgraded those in PE who were in the middle of the list. This is why I was totally surprised that this May both my wife and I were op-upped from PE to J when flying BA LHR-JFK on a BA-issued ticket.

Domestic flights are a different ballgame because you should by policy for sure be after every single AA elite, since AA elites are entitled to complimentary upgrades (unless they have more than one companion or a few other exceptions). On long haul international, AA elites at least aren’t automatically eligible for upgrades without an instrument, so I’d think BA elites’ chances would be somewhat higher, all else being equal (which it seldom is). An AA Gold should cry foul if a BA elite is upgraded before them on a domestic flight but has no right to complain on an international.

AS 75K OpUped from P-E to J on AA in May. PE was oversold but J went out with a few empty seats.

It's the op downs that make me lose sleep at night.

As well as AS MVPG75K & MVPG100K.

As an AS 100K, I flew AA LAX-MIA return on the 77W. Upgrade cleared on the outbound at T-72. On the return, I was #1 on the waitlist but dropped to #2 shortly before boarding. I waited for Group 2 boarding - I was in PE sold as MCE anyway. When the gate agent scanned my boarding pass, the system beeped and spat out a J boarding pass. My first op-up on AA. My PE seat was occupied upon departure.

James

It increases you chances from 0.6% to 0.8%. Hardly seems worth the effort to even discuss this anymore. :D