I'm trying to book flights back to the UK from the US for my family in October and was hoping to find flights that could be upgraded with miles as we have a lot of miles, but not enough to send all four of us business. I signed up for an Expert Flyer account and the only flights that seem to be showing that they have seat availability for upgrading with miles are the BA-operated ones, but you need to book a fare with booking class Y to qualify with BA for mileage upgrades. Expert Flyer says there are Y-class flights available to book, but the only flights showing on the AA website are Q & O. Any advice on how I go about finding elusive Y-class flights to book? Or experience with expert flyer and how accurate they are?

EF is accurate, Y should always be available if any other economy class is available.​​​​​​ You can search with matrix using the faring code "f bc=y" (without quotes).

Sorry but you have a lot of misunderstandings with your strategy.

1) You don't use EF to search for upgrade space on BA. Any C space you see on EF for a BA operated flight is completely irrelevant when it comes to upgrades.

2) The mileage upgrades you're referencing on BA require a full Y fare, as you noted, but these upgrades are only one class so even if you were to do this it would only get you to PE.

3) The full Y (and W, for upgrades from PE to business) fares are going to be prohibitively expensive, you can usually just buy discounted business (and certainly PE) for much cheaper. For example looking at a random date the full Y fare for a JFK-LHR roundtrip is $4300 each. Spending $4300 for economy then miles to upgrade to PE is a terrible deal.

Thanks so much for your insight! Do you mind if I ask a few more questions?

• I signed up for EF as I had read a recommendation (I think maybe The Points Guy) to use that site to find American Airlines (that's who my miles are with) flights to book that are eligible for upgrades with miles. Is that not something the site can do?
• What would you say is the best strategy if you want to book an American Airlines flight and upgrade to business using miles? I'm flying return LA-LON end of October with my husband and two children. Between us, my husband and I have about 400,000 AA miles

Yes, for upgrading AA marketed and operated flights with AA miles, EF can search for that space.

Book AA marketed and operated in economy, then use miles+copay upgrades.

OP:
using Expert flyer, select on the main menu:
AWARDS AND UPGRADES
then your travel dates and cities
Click the box for
Business - Upgrade (Including 2-Cabin Domestic First) (C)
or
First - Upgrade (for 3-cabin flights only) (A)
if you see a number that's greater than 0, you can upgrade that number of seats with miles and copay

Thank you! Do you have any advice regarding how to best search for flights you can upgrade with miles + copay on EF? Just keep searching different dates within the Awards and Upgrades availability section until you find a flight that shows available seats for upgrade on the far right column of the results page? I'm selecting to search for Business - Upgrade (Including 2-Cabin Domestic First) (C).

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Thanks so much! That answers my question that is still pending moderator approval perfectly!

And when using the Awards and Upgrades search you must search segment by segment to see true upgrade space.

I’m in the same boat. I have AA economy booked to LHR and want to upgrade with miles and cash. I, too, noticed that only BA seemed to have seats available for upgrade, not AA operated flights. I’m waiting till closer to the date to (7 days prior) see if seat become available for upgrade. It does make sense that they would wait closer to the travel date to make them available as it is more lucrative to sell J outright than allow upgrades for relatively paltry cash amounts.

search 7 days at a time (week by week) by selecting +/- 3 days on your search.
dont expect to find much availability for any instantly-confirmable seats. You'll likely have to waitlist. Especially if looking for FOUR of them on the same flight

I know C class has a revenue bucket and an upgrade bucket.
I'm trying to upgrade to first JFK-LAX.
I didn't realize A also has dual inventories - same as C.
Is that correct?

Yes, it is painful.

BA does not have seats to upgrade. when searching for C upgrade space, exclude codeshares and search by individual segment.

You don't mention where, in the US, you are originating. But as mentioned in this thread, search the long haul segment first (e.g. JFK-LHR, DFW-LHR, etc.). Doing a JFK-LHR search on 10/4 with the +/3 day option allows you to see a full week. I did this for 10/4, 10/11, 10/18, 10/25 and unfortunately saw no availability at this time. AA will typically open those seats up closer to departure so you could call and waitlist. Someone correct me if I'm wrong on this, but they'll take your $350 up front and give it back if the upgrade falls through. They'll also ding your account 25,000 points when the upgrade clears. It's been a while since I waitlisted. Also, make sure you don't book a basic economy fare, as those aren't eligible for point+copay upgrades.

Here are the parameters you'd need to put in your search to ensure you're seeing only AA metal. Jus keep searching iterations using other gateway cities that would be part of your routing (LAX, DFW, ORD, MIA, CLT, PHL, JFK).
Side note: I also did a search JFK-LHR for 1/15/24 +/- days and found a ton of availability. #1 - it's low season and #2 - AA likely opened those up in the past few weeks based on low sales demand.