Programs: Hhonors Gold, National Executive, Grazie Gold, Identity Platinum
AA flies direct to LHR from ORD, DFW, LAX, MIA, JFK and RDU. You'd need to route through one of these cities if you don't want to use BA. Personally, I'd probably try through MIA or DFW, and maybe have a day or two layover in one of those cities to minimize the chances of weather completely screwing up your plans.
US - Have you looked at Star Alliance partner awards too, or just direct on US? That gives you a lot more flexibility.
In both cases, I think you have to be flexible. You may not get a direct routing. You may have an additional stop along the way. As long as it's part of the same ticket, this shouldn't cost you significantly more (maybe some extra taxes/fees). Additionally, you may have to do what's called an "open jaw", where you fly into one airport and fly out of another one. An example: Let's say that you're able to find Lufthansa availability from the US to Germany, no award availability from Germany to UK and United availability from UK to US. They could still get you to Germany, and then you could book a separate ticket to get to the UK.
I understand why that's not optimal. But when you have fixed dates, you have fewer choices
My recent experience is that is is very difficult to find non-BA flights to the UK on AA. Availability is generally much better with UA. First suggestion is to subscribe to ExpertFlyer (or similar) and set up alerts for all the AA flights that work for you. In the meantime, if there are any non-BA flights near your dates, book them. At least you will have something and then you do a free date change w/AA if something perfect comes up. The holidays will be a big challenge though. Good luck
Programs: Marriott Silver, PC Gold, HH Silver, Starwood Gold, AA Plat, Avis First
Need help with US-UK award booking, AA+US availability issues, any tricks?
BA opens up its entire inventory as they have these exhorbitant taxes where they recoup almost all the money and is the same as buying a paid ticket. AA on the other hand is extremely stingy and would open very few seats and that too on non peak days only.
As long as the AMEX-Aeroplan-US trick still works, you can convert 10K AMEX MR points to 10K Aeroplan miles, and convert them to 8500 US miles via points.com. Then book on UA with your US miles. Blog post here http://thepointsguy.com/2012/08/how-...-decent-ratio/, there are also posts in the related threads here on FT.
Also check AA for AB MIA-DUS-STN, available for several dates including 12/23-1/3 for only 20K miles each way. DTW-MIA may be a problem, but you can have as long a layover as needed in MIA. Or you can use another airline to get to FLL or MIA.