Originally Posted by
SonicKryptonite
We were open to going British Airways as it was cheaper in general, but it's not showing a multi-city journey to Key West for whatever reason, so unfortunately they are ruled out.
No, they're not. You can price an open-jaw roundtrip by phoning BA. And you can also price the (cash) trip at aa.com, which will include options using BA for the trans-Atlantic flights. But AA only sells flights up to 331 days in advance, so you might have to wait a week or two before flights for your desired return date show up.
In what class of service do you plan to travel?
Award seats on many carriers are capacity-controlled -- as are the seats which other airlines make available to partners -- which would explain why they are available on some dates, but not others. You would likely be flying in and out of EYW on AA (a BA partner), or DL (a VS partner).