Hi, new to FT forum, I have picked up some great tricks from this website, but I have a burning question.

I always thought that if there is award space available you can upgrade, true ?
I hope its not a dumb question

I was gonna book a flight from ORD-LHR-JED in prem econ class. Only for the ORD-LHR leg I wanted to upgrade to business class as it was AA - which has much better biz class than BA. When I search for Awards on ORD-LHR only flight from american which shows up is AA90, the flight which BA is selling ME is AA86. AA86 doesn't show up on award search, but shows up on "book and upgrade". Does it mean that AA86 is eligible UuA ?
or
The Award search is just broken AGAIN?