Originally Posted by Tafflyer

You were lucky. That route still has plenty of availability but it will now cost you 12,000 Avios in Economy or 24,000 in US domestic First (aka Business). Using AA miles you can still have this route from 5,000 AAdvantage miles in Economy or 15,000 in First. This is a terrible devaluation from BA given that if you gain Avios from flying they are much harder to come by than AA miles.

On top of that, AA has introduced dynamic award pricing and will only show the low-cost awards to partners like BA. The effect is particularly pronounced on First and Business class award redemptions as AA and AS deliberately limit availability to increase revenue. On their own respective loyalty schemes they still make awards available but for ludicrous amounts of miles. The BA partner redemptions do not have the IT capacity to mirror AA and AS dynamic pricing so those flights are simply not available via BA.

I do have some sympathy with OP. Whilst not understanding that award availability on partners is controlled by the operating airline, we are seeing divergence of the schemes within OneWorld and BA Avios has been seriously downgraded as a result. I used to value AA miles and BA Avios both at 1c per mile/point, but I have revised my Avios valuation to 0,75c. This does not mean you can't get better value than that, but I can't as I only get Avios from flying. I don't live in the UK so have no access to Amex vouchers, double Avios promotions or Nectar points etc. Spending any given currency amount on AA flights now give a much higher redemption value than Avios.