Originally Posted by flyingeph12

1. If you are looking for next April, it's too early to book. You can only book 331 days in advance.

2. If Berlin is your desired destination, Finnair is probably your best option, since it would be one stop from SFO/LAX (i.e., SFO/LAX-HEL-BER). SFO-HEL is seasonal, however, so if you're looking for early April, LAX might be your only option. It's hard to say definitively, since Finnair has not yet published its SFO-HEL schedule for 2020 (this year SFO-HEL begins on 10 April).

3. As you've probably figured out by now, using BA for the trans-atlantic flight will result in massively high fees. Unfortunately, BA is also the most readily available option. On AA's website, when doing an advanced search, you can specify AA only. Of course, BER is not serviced by AA, so I would search SFO/LAX-LHR, and then after you've found a date that works, search for the BA flight to Berlin.

4. The above search strategy won't work for other partners, like Finnair and Iberia. But AA's search function does allow you to filter results for nonstop flights. So I would search specifically for the nonstop flight (i.e., SFO/LAX-HEL, SFO/LAX-MAD, etc.) and then the European feeder flight (i.e., HEL/MAD-BER). You can also try searching using other gateways (e.g., JFK/ORD-HEL/MAD), and search for the AA feeder flight separately.

5. As someone else has mentioned, flexibility and persistence are the keys here. I've always been able to use my miles successfully and avoid BA. But that has meant maybe shifting my dates around a little bit, or adding extra connections. I've also spent many hours searching and refining and monitoring award availability space (ExpertFlyer is good for monitoring, and a subscription might be worth it). If you don't feel like you have the time, it might be worth looking into using an award booking service.

6. BA gets a lot of hate here (and as I said, I've never used them on an award). But BA could make sense in certain situations. First, BA is readily available, so if your dates are not flexible, they might make sense. Second, BA serves a ton of destinations in Europe, so if you want to minimize connections, BA is a good option. Finally, your original thought was to buy a ticket and upgrade using AA miles. Assuming there is upgrade space and you're not purchasing a full-fare ticket, that option roundtrip would have cost you per person 50,000 miles + $700 + cost of an economy ticket. Depending on how much you value AA miles (both the extra miles for the award, and the miles given up by booking an award instead of a revenue ticket), a BA award may not be that more expensive than the upgrade option (and likely easier to find).